Acute and chronic saturated fatty acid treatment as a key instigator of the TLR-mediated inflammatory response in human adipose tissue, in vitro

Metformin plus L-carnitine enhances brown/beige adipose tissue activity via Nrf2/HO-1 signaling to reduce lipid accumulation and inflammation in murine obesity

This study investigated how Metformin (Met) combined with L-carnitine (L-car) modulates brown adipose tissue (BAT) to affect obesity. High-fat-induced obese rats received daily oral gavage with Met and/or L-car, followed by serum biochemical analysis, histopathological observation on adipose tissues, and immunochemistry test for the abdominal expression of BAT-specific uncoupling protein 1 (UCP1). Mouse-embryonic-fibroblast cells were induced into adipocytes, during which Met plus L-car was added with/without saturated fatty acid (SFA). The role of nuclear factor erythroid 2-related factor 2 (Nrf2) in adipocyte browning was investigated by gene silencing. Mitochondria biogenesis in adipocytes was inspected by Mitotracker staining. Nrf2/heme oxygenase-1 (HO-1)/BAT-related genes/proinflammatory marker expressions in adipose tissues and/or adipocytes were analyzed by Western blot, qRT-PCR, and/or immunofluorescence test. Met or L-car improved metabolic disorders, reduced adipocyte vacuolization and swelling, upregulated levels of BAT-related genes including UCP1 and downregulated proinflammatory marker expressions, and activated the Nrf2/HO-1 pathway in adipose tissues of obese rats. Met and L-car functioned more strongly than alone. In adipocytes, Met plus L-car upregulated BAT-related gene levels and protected against SFA-caused inflammation promotion and mitochondria degeneration, which yet was attenuated by Nrf2 silencing. Met plus L-car enhances BAT activity and white adipose tissue browning via the Nrf2/HO-1 pathway to reduce lipid accumulation and inflammation in obese rats.

From the Sun to the Cell: Examining Obesity through the Lens of Vitamin D and Inflammation

Obesity affects more than one billion people worldwide and often leads to cardiometabolic chronic comorbidities. It induces senescence-related alterations in adipose tissue, and senescence is closely linked to obesity. Fully elucidating the pathways through which vitamin D exerts anti-inflammatory effects may improve our understanding of local adipose tissue inflammation and the pathogenesis of metabolic disorders. In this narrative review, we compiled and analyzed the literature from diverse academic sources, focusing on recent developments to provide a comprehensive overview of the effect of vitamin D on inflammation associated with obesity and senescence. The article reveals that the activation of the NF-κB (nuclear factor kappa B subunit 1) and NLRP3 inflammasome (nucleotide-binding domain, leucine-rich-containing, pyrin domain-containing-3) pathways through the toll-like receptors, which increases oxidative stress and cytokine release, is a common mechanism underlying inflammation associated with obesity and senescence, and it discusses the potential beneficial effect of vitamin D in alleviating the development of subclinical inflammation. Investigating the main target cells and pathways of vitamin D action in adipose tissue could help uncover complex mechanisms of obesity and cellular senescence. This review summarizes significant findings related to opportunities for improving metabolic health.

CD36 favours fat sensing and transport to govern lipid metabolism

CD36, located on the cell membrane, transports fatty acids in response to dietary fat. It is a critical fatty acid sensor and regulator of lipid metabolism. The interaction between CD36 and lipid dysmetabolism and obesity has been identified in various models and human studies. Nevertheless, the mechanisms by which CD36 regulates lipid metabolism and the role of CD36 in metabolic diseases remain obscure. Here, we summarize the latest research on the role of membrane CD36 in fat metabolism, with emphasis on CD36-mediated fat sensing and transport. This review also critically discusses the factors affecting the regulation of CD36-mediated fat dysfunction. Finally, we review previous clinical evidence of CD36 in metabolic diseases and consider the path forward.

Adipose microtissue-on-chip: a 3D cell culture platform for differentiation, stimulation, and proteomic analysis of human adipocytes

Human fat tissue has evolved to serve as a major energy reserve. An imbalance between energy intake and expenditure leads to an expansion of adipose tissue. Maintenance of this energy imbalance over long periods leads to obesity and metabolic disorders such as type 2 diabetes, for which a clinical cure is not yet available. In this study, we developed a microfluidic large-scale integration chip platform to automate the formation, long-term culture, and retrieval of 3D adipose microtissues to enable longitudinal studies of adipose tissue in vitro. The chip was produced from soft-lithography molds generated by 3D-printing, which allowed scaling of pneumatic membrane valves for parallel fluid routing and thus incorporated microchannels with variable dimensions to handle 3D cell cultures with diameters of several hundred micrometers. In 32 individual fluidically accessible cell culture chambers, designed to enable the self-aggregation process of three microtissues, human adipose stem cells differentiated into mature adipocytes over a period of two weeks. Coupling mass spectrometry to the cell culture platform, we determined the minimum cell numbers required to obtain robust and complex proteomes with over 1800 identified proteins. The adipose microtissues on the chip platform were then used to periodically simulate food intake by alternating the glucose level in the cell-feeding media every 6 h over the course of one week. The proteomes of adipocytes under low/high glucose conditions exhibited unique protein profiles, confirming the technical functionality and applicability of the chip platform. Thus, our adipose tissue-on-chip in vitro model may prove useful for elucidating the molecular and functional mechanisms of adipose tissue in normal and pathological conditions, such as obesity.

Asthma and obesity: endotoxin another insult to add to injury?

Low-grade inflammation is often an underlying cause of several chronic diseases such as asthma, obesity, cardiovascular disease, and type 2 diabetes mellitus (T2DM). Defining the mediators of such chronic low-grade inflammation often appears dependent on which disease is being investigated. However, downstream systemic inflammatory cytokine responses in these diseases often overlap, noting there is no doubt more than one factor at play to heighten the inflammatory response. Furthermore, it is increasingly believed that diet and an altered gut microbiota may play an important role in the pathology of such diverse diseases. More specifically, the inflammatory mediator endotoxin, which is a complex lipopolysaccharide (LPS) derived from the outer membrane cell wall of Gram-negative bacteria and is abundant within the gut microbiota, and may play a direct role alongside inhaled allergens in eliciting an inflammatory response in asthma. Endotoxin has immunogenic effects and is sufficiently microscopic to traverse the gut mucosa and enter the systemic circulation to act as a mediator of chronic low-grade inflammation in disease. Whilst the role of endotoxin has been considered in conditions of obesity, cardiovascular disease and T2DM, endotoxin as an inflammatory trigger in asthma is less well understood. This review has sought to examine the current evidence for the role of endotoxin in asthma, and whether the gut microbiota could be a dietary target to improve disease management. This may expand our understanding of endotoxin as a mediator of further low-grade inflammatory diseases, and how endotoxin may represent yet another insult to add to injury.

Dietary Fatty Acids at the Crossroad between Obesity and Colorectal Cancer: Fine Regulators of Adipose Tissue Homeostasis and Immune Response

Colorectal cancer (CRC) is among the major threatening diseases worldwide, being the third most common cancer, and a leading cause of death, with a global incidence expected to increase in the coming years. Enhanced adiposity, particularly visceral fat, is a major risk factor for the development of several tumours, including CRC, and represents an important indicator of incidence, survival, prognosis, recurrence rates, and response to therapy. The obesity-associated low-grade chronic inflammation is thought to be a key determinant in CRC development, with the adipocytes and the adipose tissue (AT) playing a significant role in the integration of diet-related endocrine, metabolic, and inflammatory signals. Furthermore, AT infiltrating immune cells contribute to local and systemic inflammation by affecting immune and cancer cell functions through the release of soluble mediators. Among the factors introduced with diet and enriched in AT, fatty acids (FA) represent major players in inflammation and are able to deeply regulate AT homeostasis and immune cell function through gene expression regulation and by modulating the activity of several transcription factors (TF). This review summarizes human studies on the effects of dietary FA on AT homeostasis and immune cell functions, highlighting the molecular pathways and TF involved. The relevance of FA balance in linking diet, AT inflammation, and CRC is also discussed. Original and review articles were searched in PubMed without temporal limitation up to March 2021, by using fatty acid as a keyword in combination with diet, obesity, colorectal cancer, inflammation, adipose tissue, immune cells, and transcription factors.

Contribution of the Microbiota and their Secretory Products to Inflammation and Colorectal Cancer Pathogenesis: The Role of Toll-like Receptors

Alterations in diversity and function of the gut microbiome are associated with concomitant changes in immune response, including chronic inflammation. Chronic inflammation is a major risk factor for colorectal cancer (CRC). An important component of the inflammatory response system are the toll-like receptors (TLRs). TLRs are capable of sensing microbial components, including nucleic acids, lipopolysaccharides, and peptidoglycans, as well as bacterial outer membrane vesicles (OMV). OMVs can be decorated with or carry as cargo these TLR activating factors. These microbial factors can either promote tolerance or activate signaling pathways leading to chronic inflammation. Herein we discuss the role of the microbiome and the OMVs that originate from intestinal bacteria in promoting chronic inflammation and the development of colitis-associated CRC. We also discuss the contribution of TLRs in mediating the microbiome-inflammation axis and subsequent cancer development. Understanding the role of the microbiome and its secretory factors in TLR response may lead to the development of better cancer therapeutics.

Chronic and Transient Hyperglycemia Induces Changes in the Expression Patterns of IL6 and ADIPOQ Genes and Their Associated Epigenetic Modifications in Differentiating Human Visceral Adipocytes

Adipokines secreted by hypertrophic visceral adipose tissue (VAT) instigate low-grade inflammation, followed by hyperglycemia (HG)-related metabolic disorders. The latter may develop with the participation of epigenetic modifications. Our aim was to assess how HG influences selected epigenetic modifications and the expression of interleukin 6 (IL-6) and adiponectin (APN; gene symbol ADIPOQ) during the adipogenesis of human visceral preadipocytes (HPA-v). Adipocytes (Ads) were chronically or transiently HG-treated during three stages of adipogenesis (proliferation, differentiation, maturation). We measured adipokine mRNA, protein, proven or predicted microRNA expression (RT-qPCR and ELISA), and enrichment of H3K9/14ac, H3K4me3, and H3K9me3 at gene promoter regions (chromatin immunoprecipitation). In chronic HG, we detected different expression patterns of the studied adipokines at the mRNA and protein levels. Chronic and transient HG-induced changes in miRNA (miR-26a-5p, miR-26b-5p, let-7d-5p, let-7e-5p, miR-365a-3p, miR-146a-5p) were mostly convergent to altered IL-6 transcription. Alterations in histone marks at the IL6 promoter were also in agreement with IL-6 mRNA. The open chromatin marks at the ADIPOQ promoter mostly reflected the APN transcription during NG adipogenesis, while, in the differentiation stage, HG-induced changes in all studied marks were in line with APN mRNA levels. In summary, HG dysregulated adipokine expression, promoting inflammation. Epigenetic changes coexisted with altered expression of adipokines, especially for IL-6; therefore, epigenetic marks induced by transient HG may act as epi-memory in Ads. Such changes in the epigenome and expression of adipokines could be instrumental in the development of inflammation and metabolic deregulation of VAT.

Expression profiling and analysis of some miRNAs in subcutaneous white adipose tissue during development of obesity

Background

MicroRNAs are emerging as new mediators in the regulation of adipocyte physiology and have been approved to play a role in obesity. Despite several studies have focused on microRNA expression profiles and functions in different metabolic tissues, little is known about their response to nutritional interventions in white adipose tissue during obesity stages, and whether they differ in this response to weight-reduction strategy is poorly understood. Our objectives were to study the dysregulation of some miRNAs in subcutaneous inguinal white adipose tissue during weight change, expansion/reduction; in response to both a high-fat diet and switching to a normal diet feeding, and to evaluate them as potential biomarkers and therapeutic targets for early obesity management

Method

A hundred 6-week-old male Wister rats were randomly divided into a normal diet group (N.D), a high-fat diet group (H.F.D), and a switched to a normal diet group (H.F.D/N.D). At the beginning and at intervals 2 weeks, serum lipid, hormone levels, total body fat mass, and inguinal subcutaneous white adipose tissue mass (WAT) measurements were recorded using dual-energy X-ray absorptiometry (DEXA). The expression levels of microRNAs were evaluated using real-time PCR.

Results

Significant alterations were observed in serum glucose, lipid profile, and adipokine hormones during the early stages of obesity development. Alteration in rno-mir 30a-5p, rno-mir 133a-5p, and rno-mir 107-5p expression levels were observed at more than one time point. While rno-let-7a-5p, rno-mir 193a-5p, and rno-mir125a-5p were downregulated and rno-mir130a-5p was upregulated at all time points within 2 to 4 weeks in response to H.F.D feeding for 10 weeks. The impact of switching to normal diet has a reversed effect on lipid profile, adipokine hormone levels, and some miRNAs. The bioinformatics results have identified a novel and important pathway related to inflammatory signalling.

Conclusion

Our research demonstrated significant alterations in some adipocyte-expressed miRNAs after a short time of high caloric diet consumption. This provides further evidence of the significant role of nutrition as an epigenetic factor in regulation of lipid and glucose metabolism genes by modulating of related key miRNAs. Therefore, we suggest that miRNAs could be used as biomarkers for adiposity during diet-induced obesity. Perhaps limitation in calories intake is a way to manipulate obesity and associated metabolic disorders. Further studies are needed to fully elucidate the role of microRNAs in the development of obesity

Insights Into the Role of Mitochondrial Ion Channels in Inflammatory Response

Mitochondria are the source of many pro-inflammatory signals that cause the activation of the immune system and generate inflammatory responses. They are also potential targets of pro-inflammatory mediators, thus triggering a severe inflammatory response cycle. As mitochondria are a central hub for immune system activation, their dysfunction leads to many inflammatory disorders. Thus, strategies aiming at regulating mitochondrial dysfunction can be utilized as a therapeutic tool to cure inflammatory disorders. Two key factors that determine the structural and functional integrity of mitochondria are mitochondrial ion channels and transporters. They are not only important for maintaining the ionic homeostasis of the cell, but also play a role in regulating reactive oxygen species generation, ATP production, calcium homeostasis and apoptosis, which are common pro-inflammatory signals. The significance of the mitochondrial ion channels in inflammatory response is still not clearly understood and will need further investigation. In this article, we review the different mechanisms by which mitochondria can generate the inflammatory response as well as highlight how mitochondrial ion channels modulate these mechanisms and impact the inflammatory processes.

The Exercise Training Modulatory Effects on the Obesity-Induced Immunometabolic Dysfunctions

Reduced physical activity rate in people's lifestyle is a global concern associated with the prevalence of health disorders such as obesity and metabolic disturbance. Ample evidence has indicated a critical role of the immune system in the aggravation of obesity. The type, duration, and production of adipose tissue-released mediators may change subsequent inactive lifestyle-induced obesity, leading to the chronic systematic inflammation and monocyte/macrophage (MON/MФ) phenotype polarization. Preliminary adipose tissue expansion can be inhibited by changing the lifestyle. In this context, exercise training is widely recommended due to a definite improvement of energy balance and the potential impacts on the inflammatory signaling cascades. How exercise training affects the immune system has not yet been fully elucidated, because its anti-inflammatory, pro-inflammatory, or even immunosuppressive impacts have been indicated in the literature. A thorough understanding of the mechanisms triggered by exercise can suggest a new approach to combat meta-inflammation-induced metabolic diseases. In this review, we summarized the obesity-induced inflammatory pathways, the roles of MON/MФ polarization in adipose tissue and systemic inflammation, and the underlying inflammatory mechanisms triggered by exercise during obesity.

Palmitic acid is an intracellular signaling molecule involved in disease development

Emerging evidence shows that palmitic acid (PA), a common fatty acid in the human diet, serves as a signaling molecule regulating the progression and development of many diseases at the molecular level. In this review, we focus on its regulatory roles in the development of five pathological conditions, namely, metabolic syndrome, cardiovascular diseases, cancer, neurodegenerative diseases, and inflammation. We summarize the clinical and epidemiological studies; and also the mechanistic studies which have identified the molecular targets for PA in these pathological conditions. Activation or inactivation of these molecular targets by PA controls disease development. Therefore, identifying the specific targets and signaling pathways that are regulated by PA can give us a better understanding of how these diseases develop for the design of effective targeted therapeutics.

A Mechanistic Model of Gut-Brain Axis Perturbation and High-Fat Diet Pathways to Gut Microbiome Homeostatic Disruption, Systemic Inflammation, and Type 2 Diabetes

Type 2 diabetes (T2D) is a highly prevalent metabolic disease, affecting nearly 10% of the American population. Although the etiopathogenesis of T2D remains poorly understood, advances in DNA sequencing technologies have allowed for sophisticated interrogation of the human microbiome, providing insight into the role of the gut microbiome in the development and progression of T2D. An emerging body of research reveals that gut-brain axis (GBA) perturbations and a high-fat diet (HFD), along with other modifiable and nonmodifiable risk factors, contribute to gut microbiome homeostatic imbalance. Homeostatic imbalance or disruption increases gut wall permeability and facilitates translocation of endotoxins (lipopolysaccharides) into the circulation with resultant systemic inflammation. Chronic, low-grade systemic inflammation ensues with pro-inflammatory pathways activated, contributing to obesity, insulin resistance (IR), pancreatic β-cell decline, and, thereby, T2D. While GBA perturbations and HFD are implicated in provoking these conditions, prior mechanistic models have tended to examine HFD and GBA pathways exclusively without considering their shared pathways to T2D. Addressing this gap, this article proposes a mechanistic model informed by animal and human studies to advance scientific understanding of (1) modifiable and nonmodifiable risk factors for gut microbiome homeostatic disruption, (2) HFD and GBA pathways contributing to homeostatic disruption, and (3) shared GBA and HFD pro-inflammatory pathways to obesity, IR, β-cell decline, and T2D. The proposed mechanistic model, based on the extant literature, proposes a framework for studying the complex relationships of the gut microbiome to T2D to advance study in this promising area of research.

Macronutrients and the Adipose-Liver Axis in Obesity and Fatty Liver

Macronutrient metabolism is a highly orchestrated process, with adipose tissue and liver each playing central roles in nutrient uptake, processing, transport, and storage. These 2 tissues form an important metabolic circuit, particularly as it relates to lipids as the primary storage form of excess energy. The function of the circuit is influenced by many factors, including the quantity and type of nutrients consumed and their impact on the overall health of the tissues. In this review we begin with a brief summary of the homeostatic disposition of lipids between adipose tissue and liver and how these processes can become dysregulated in obesity. We then explore how specific dietary nutrients and nutrient combinations can exert unique influences on the liver-adipose tissue axis.

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.

The Effect and Mechanism of KLF7 in the TLR4/NF-κB/IL-6 Inflammatory Signal Pathway of Adipocytes

Objective

To investigate the role and possible molecular mechanism of Krüppel-like factor 7 (KLF7) in the TLR4/NF-κB/IL-6 inflammatory signaling pathway activated by free fatty acids (FFA).

Methods

The mRNA and protein expression levels of KLF7 and the factors of TLR4/NF-κB/IL-6 inflammatory signal pathways were detected by qRT-PCR and Western blotting after cell culture with different concentrations of palmitic acid (PA). The expression of KLF7 or TLR4 in adipocytes was upregulated or downregulated; after that, the mRNA and protein expression levels of these key factors were detected. KLF7 expression was downregulated while PA stimulated adipocytes, and then the mRNA and protein expressions of KLF7/p65 and downstream inflammatory cytokine IL-6 were detected. The luciferase reporter assay was used to determine whether KLF7 had a transcriptional activation effect on IL-6.

Results

(1) High concentration of PA can promote the expression of TLR4, KLF7, and IL-6 in adipocytes. (2) TLR4 positively regulates KLF7 expression in adipocytes. (3) KLF7 positively regulates IL-6 expression in adipocytes. (4) PA promotes IL-6 expression via KLF7 in adipocytes. (5) KLF7 has a transcriptional activation on IL-6.

Conclusion

PA promotes the expression of the inflammatory cytokine IL-6 by activating the TLR4/KLF7/NF-κB inflammatory signaling pathway. In addition, KLF7 may directly bind to the IL-6 promoter region and thus activate IL-6.

Hyperglycemia Affects miRNAs Expression Pattern during Adipogenesis of Human Visceral Adipocytes-Is Memorization Involved?

microRNAs are increasingly analyzed in adipogenesis, whose deregulation, especially visceral, contributes to the development of diabetes. Hyperglycemia is known to affect cells while occurring acutely and chronically. Therefore, we aimed to evaluate the effect of hyperglycemia on human visceral pre/adipocytes from the perspective of microRNAs. The relative expression of 78 microRNAs was determined by TaqMan Low Density Arrays at three stages of HPA-v adipogenesis conducted under normoglycemia, chronic, and intermittent hyperglycemia (30 mM). Hierarchical clustering/Pearson correlation revealed the relationship between various microRNAs' expression profiles, while functional analysis identified the genes and signaling pathways regulated by differentially expressed microRNAs. Hyperglycemia affected microRNAs' expression patterns during adipogenesis, and at the stage of pre-adipocytes, differentiated and matured adipocytes compared to normoglycemia. Interestingly, the changes that were evoked upon hyperglycemic exposure during one adipogenesis stage resembled those observed upon chronic hyperglycemia. At least 15 microRNAs were modulated during normoglycemic and/or hyperglycemic adipogenesis and/or upon intermittent/chronic hyperglycemia. Bioinformatics analysis revealed the involvement of these microRNAs in cell cycles, lipid metabolism, ECM⁻receptor interaction, oxidative stress, signaling of insulin, MAPK, TGF-β, p53, and more. The obtained data suggests that visceral pre/adipocytes exposed to chronic/intermittent hyperglycemia develop a microRNAs' expression pattern, which may contribute to further visceral dysfunction, the progression of diabetic phenotype, and diabetic complications possibly involving "epi"-memory.

The role of noninvasive cardiovascular testing, applied clinical nutrition and nutritional supplements in the prevention and treatment of coronary heart disease

Numerous clinical trials suggest that we have reached a limit in our ability to decrease the incidence of coronary heart disease (CHD) and cardiovascular disease (CVD) utilizing the traditional diagnostic evaluation, prevention and treatment strategies for the top five cardiovascular risk factors of hypertension, diabetes mellitus, dyslipidemia, obesity and smoking. About 80% of heart disease (heart attacks, angina, coronary heart disease and congestive heart failure) can be prevented by optimal nutrition, optimal exercise, optimal weight and body composition, mild alcohol intake and avoiding smoking. Statistics show that approximately 50% of patients continue to have CHD or myocardial infarction (MI) despite presently defined 'normal' levels of the five risk factors listed above. This is often referred to as the 'CHD gap'. Novel and more accurate definitions and evaluations of these top five risk factors are required, such as 24 h ambulatory blood pressure (ABM) results, advanced lipid profiles, redefined fasting and 2 h dysglycemia parameters, a focus on visceral obesity and body composition and the effects of adipokines on cardiovascular risk. There are numerous traumatic insults from the environment that damage the cardiovascular system but there are only three finite vascular endothelial responses, which are inflammation, oxidative stress and immune vascular dysfunction. In addition, the concept of translational cardiovascular medicine is mandatory in order to correlate the myriad of CHD risk factors to the presence or absence of functional or structural damage to the vascular system, preclinical and clinical CHD. This can be accomplished by utilizing advanced and updated CV risk scoring systems, new and redefined CV risk factors and biomarkers, micronutrient testing, cardiovascular genetics, nutrigenomics, metabolomics, genetic expression testing and noninvasive cardiovascular testing.

Nutrients and Oxidative Stress: Friend or Foe?

There are different types of nutritionally mediated oxidative stress sources that trigger inflammation. Much information indicates that high intakes of macronutrients can promote oxidative stress and subsequently contribute to inflammation via nuclear factor-kappa B- (NF-κB-) mediated cell signaling pathways. Dietary carbohydrates, animal-based proteins, and fats are important to highlight here because they may contribute to the long-term consequences of nutritionally mediated inflammation. Oxidative stress is a central player of metabolic ailments associated with high-carbohydrate and animal-based protein diets and excessive fat consumption. Obesity has become an epidemic and represents the major risk factor for several chronic diseases, including diabetes, cardiovascular disease (CVD), and cancer. However, the molecular mechanisms of nutritionally mediated oxidative stress are complex and poorly understood. Therefore, this review aimed to explore how dietary choices exacerbate or dampen the oxidative stress and inflammation. We also discussed the implications of oxidative stress in the adipocyte and glucose metabolism and obesity-associated noncommunicable diseases (NCDs). Taken together, a better understanding of the role of oxidative stress in obesity and the development of obesity-related NCDs would provide a useful approach. This is because oxidative stress can be mediated by both extrinsic and intrinsic factors, hence providing a plausible means for the prevention of metabolic disorders.

Recent Science and Clinical Application of Nutrition to Coronary Heart Disease

One of the greatest threats to mortality in industrialized societies continues to be coronary heart disease (CHD). Moreover, the ability to decrease the incidence of CHD has reached a limit utilizing traditional diagnostic evaluations and prevention and treatment strategies for the top five cardiovascular risk factors (hypertension, diabetes mellitus, dyslipidemia, obesity, and smoking). It is well known that about 80% of CHD can be prevented with optimal nutrition, coupled with exercise, weight management, mild alcohol intake, and smoking cessation. Among all of these factors, optimal nutrition provides the basic foundation for prevention and treatment of CHD. Numerous prospective nutrition clinical trials have shown dramatic reductions in the incidence of CHD. As nutritional science and nutrigenomics research continues, our ability to adjust the best nutrition with an individualized approach is emerging. This article reviews the role of nutrition in the prevention and treatment of CHD and myocardial infarction (MI).

Role of MicroRNA Regulation in Obesity-Associated Breast Cancer: Nutritional Perspectives

Breast cancer is the most common malignancy diagnosed in women, and the incidence of breast cancer is increasing every year. Obesity has been identified as one of the major risk factors for breast cancer progression. The mechanisms by which obesity contributes to breast cancer development is not yet understood; however, there are a few mechanisms counted as potential producers of breast cancer in obesity, including insulin resistance, chronic inflammation and inflammatory cytokines, adipokines, and sex hormones. Recent emerging evidence suggests that alterations in microRNA (miRNA) expressions are found in several diseases, including breast cancer and obesity; however, miRNA roles in obesity-linked breast cancer are beginning to unravel. miRNAs are thought to be potential noninvasive biomarkers for diagnosis and prognosis of cancer patients with comorbid conditions of obesity as well as therapeutic targets. Recent studies have evidenced that nutrients and other dietary factors protect against cancer and obesity through modulation of miRNA expressions. Herein, we summarize a comprehensive overview of up-to-date information related to miRNAs and their molecular targets involved in obesity-associated breast cancer. We also address the mechanisms by which dietary factors modulate miRNA expression and its protective roles in obesity-associated breast cancer. It is hoped that this review would provide new therapeutic strategies for the treatment of obesity-associated breast cancer to reduce the burden of breast cancer.

Effect of High Glucose Levels on White Adipose Cells and Adipokines-Fuel for the Fire

White adipocytes release adipokines that influence metabolic and vascular health. Hypertrophic obesity is associated with adipose tissue malfunctioning, leading to inflammation and insulin resistance. When pancreatic islet β cells can no longer compensate, the blood glucose concentration rises (hyperglycemia), resulting in type 2 diabetes. Hyperglycaemia may further aggravate adipose cell dysfunction in ~90% of patients with type 2 diabetes who are obese or overweight. This review will focus on the effects of high glucose levels on human adipose cells and the regulation of adipokines.

Effects of dyslipidaemia on monocyte production and function in cardiovascular disease

Monocytes are heterogeneous effector cells involved in the maintenance and restoration of tissue integrity. Monocytes and macrophages are involved in cardiovascular disease progression, and are associated with the development of unstable atherosclerotic plaques. Hyperlipidaemia can accelerate cardiovascular disease progression. However, monocyte responses to hyperlipidaemia are poorly understood. In the past decade, accumulating data describe the relationship between the dynamic blood lipid environment and the heterogeneous circulating monocyte pool, which might have profound consequences for cardiovascular disease. In this Review, we explore the updated view of monocytes in cardiovascular disease and their relationship with macrophages in promoting the homeostatic and inflammatory responses related to atherosclerosis. We describe the different definitions of dyslipidaemia, highlight current theories on the ontogeny of monocyte heterogeneity, discuss how dyslipidaemia might alter monocyte production, and explore the mechanistic interface linking dyslipidaemia with monocyte effector functions, such as migration and the inflammatory response. Finally, we discuss the role of dietary and endogenous lipid species in mediating dyslipidaemic responses, and the role of these lipids in promoting the risk of cardiovascular disease through modulation of monocyte behaviour.

Interleukin-6 is associated with chronic hyperglycemia and insulin resistance in patients after acute pancreatitis

BACKGROUND

Diabetes is a pervasive disease, with a mounting prevalence and burden on health care systems. Under this collective term of diabetes falls diabetes after diseases of the exocrine pancreas, a condition which was previously under-recognised and often mislabeled as type 2 diabetes mellitus and is now increasingly acknowledged as a stand-alone entity. However, there is a paucity of clinical studies investigating the underlying pathophysiology of diabetes after acute pancreatitis, the most frequent disease of the pancreas. This study aimed to investigate the role of adipocytokines in glucose metabolism after acute pancreatitis.

METHODS

This was a cross-sectional follow-up study of a patient cohort diagnosed with acute pancreatitis. Fasting venous blood samples were collected to analyse markers of glucose metabolism (fasting blood glucose, haemoglobin A1c, homeostasis model assessment (HOMA-IR) as a measure of insulin resistance) and adypocytokines (adiponectin, interleukin-6, leptin, monocyte chemoattractant protein-1, retinol binding protein-4, resistin, and tumor necrosis factor-α). Participants were categorized into two groups: normoglycemia after acute pancreatitis and chronic hyperglycemia after acute pancreatitis (CHAP). Binary logistic regression and linear regression analyses were used to investigate the association between each of the adipocytokines and markers of glucose metabolism. Potential confounders were adjusted for in multivariate analyses.

RESULTS

A total of 83 patients with acute pancreatitis were included, of whom 19 developed CHAP. Interleukin-6 was significantly associated with CHAP in both unadjusted and adjusted models (p = 0.030 and p = 0.018, respectively). Further, it was also significantly associated with HOMA-IR in both unadjusted and adjusted models (p = 0.029 and p = 0.037, respectively). Other adipocytokines were not significantly associated with markers of glucose metabolism.

CONCLUSION

Interleukin-6 appears to be implicated in the development of chronic hyperglycemia and insulin resistance in patients after acute pancreatitis. It may become a potential target in the prevention and early treatment of diabetes after diseases of the exocrine pancreas.

Lipopolysaccharide binding protein is an adipokine involved in the resilience of the mouse adipocyte to inflammation

AIMS/HYPOTHESIS

Lipopolysaccharide (LPS) binding protein (LBP) is a novel 65 kDa adipokine, linked to adipose tissue (AT) inflammation, obesity and insulin resistance, that inhibits adipocyte differentiation. Here, we investigated the molecular mechanisms behind these detrimental effects on adipogenesis through whole-genome transcriptomics and in vitro experiments.

METHODS

Permanent and transient knockdown (KD) and co-culture experiments were performed in 3T3-L1 and 3T3-F442A cell lines during adipocyte differentiation. Microarray gene expression was performed using Genechip Affymetrix technology and validated by real-time PCR.

RESULTS

LBP KD of 3T3-L1 cells led to a potentiated adipocyte differentiation with a dose-response relationship; genes involved in mitochondrial biogenesis, fatty acid metabolism and peroxisome proliferator-activated receptor γ (PPAR-γ) action were dramatically upregulated in parallel to increased insulin signalling. Cells with LBP KD became refractory to proinflammatory cytokines and other inflammatory stimuli (LPS and palmitate). This phenotype, mediated through disrupted nuclear factor κB (NFκB) signalling, was reversed by a soluble factor present in a co-culture with native cells and by exogenous LBP. Double-silencing of LBP and toll-like receptor 4 (TLR4) again rendered these cells insensitive to co-culture, LBP and inflammatory factors.

CONCLUSIONS/INTERPRETATION

In summary, LBP is a proinflammatory soluble adipokine that acts as a brake for adipogenesis, strengthening the negative effects of palmitate and LPS on adipocyte differentiation.

Postprandial Effect of a High-Fat Meal on Endotoxemia in Arab Women with and without Insulin-Resistance-Related Diseases

This study determined the effects of a high-fat meal on circulating endotoxin and cardiometabolic indices in adult Arab women. The cohort consisted of 92 consenting Saudi women (18 non-diabetic (ND)) control subjects; Age 24.4 ± 7.9 year; body mass index (BMI) 22.2 ± 2.2 Kg/m2), 24 overweight/obese (referred to as overweight-plus (overweight+)) subjects (Age 32.0 ± 7.8 year; BMI 28.5 ± 1.5 Kg/m2) and 50 type 2 diabetes mellitus (T2DM) patients (Age 41.5 ± 6.2 year; BMI 35.2 ± 7.7 Kg/m2). All were given a high-fat meal (standardized meal: 75 g fat, 5 g carbohydrate, 6 g protein) after an overnight fast of 12-14 h. Anthropometrics were obtained and fasting blood glucose, lipids, and endotoxin were serially measured for four consecutive postprandial hours. Endotoxin levels were significantly elevated prior to a high-fat meal in the overweight+ and T2DM than the controls (p < 0.05). Furthermore, the postprandial cardiometabolic changes led to a more detrimental risk profile in T2DM subjects than other groups, with serial changes most notable in glucose, triglycerides, high density lipoprotein-cholesterol (HDL-cholesterol), and insulin levels (p-values < 0.05). The same single meal given to subjects with different metabolic states had varying impacts on cardiometabolic health. Endotoxemia is exacerbated by a high-fat meal in Arab subjects with T2DM, accompanied by a parallel increase in cardiometabolic risk profile, suggesting disparity in disease pathogenesis of those with or without T2DM through the altered cardiometabolic risk profile rather than variance in metabolic endotoxinaemia with a high-fat meal.

Contrasting association of circulating sCD14 with insulin sensitivity in non-obese and morbidly obese subjects

SCOPE

In experimental studies, moderate to high concentrations of sCD14 (serum cluster of differentiation 14 protein) prevent lipopolysaccharide (LPS)-induced systemic inflammation, while low concentrations may promote inflammation. Given that metabolic endotoxemia is thought to initiate high-fat diet-induced insulin resistance, we explored the association between sCD14 concentrations and insulin sensitivity in humans.

METHODS AND RESULTS

Healthy non-obese (n = 12, BMI 26 ± 5y), obese (n = 11, BMI 33.45 ± 3.2) and morbidly obese participants (n = 38, BMI 45 ± 7) underwent measurement of body composition (dual energy X-ray absorptiometry) and a hyperinsulinemic-euglycemic clamp to measure insulin sensitivity (M value). Circulating sCD14 concentrations were measured by ELISA. Non-obese participants had lower circulating sCD14 concentrations compared to obese (p = 0.03). Circulating sCD14 concentrations were positively associated with percent body fat, waist circumference and white blood cell count and negatively associated with insulin sensitivity. In contrast, circulating sCD14 were positively associated with insulin sensitivity in morbidly obese participants. In regression analysis, insulin sensitivity (r = 0.52, p = 0.004) and fasting triglycerides (r = 0.49, p = 0.005) contributed independently to circulating sCD14 variance after controlling for age, sex and BMI in these morbidly obese subjects.

CONCLUSION

These findings suggest that circulating sCD14 concentrations, through its compensatory (in non-obese subjects) or buffering role (in morbidly obese subjects), could exert an important role in modulating insulin sensitivity.

[Low-grade systemic inflammation and the development of metabolic diseases: from the molecular evidence to the clinical practice]

BACKGROUND

Systemic inflammation is characterised by high circulating levels of inflammatory cytokines and increased macrophage infiltration in peripheral tissues. Most importantly, this inflammatory state does not involve damage or loss of function of the infiltrated tissue, which is a distinctive feature of the low-grade systemic inflammation. The term "meta-inflammation" has also been used to refer to the low-grade systemic inflammation due to its strong relationship with the development of cardio-metabolic diseases in obesity.

OBJECTIVE

A review is presented on the recent clinical and experimental evidence concerning the role of adipose tissue inflammation as a key mediator of low-grade systemic inflammation. Furthermore, the main molecular mechanisms involved in the inflammatory polarization of macrophages with the ability to infiltrate both the adipose tissue and the vascular endothelium via activation of toll-like receptors by metabolic damage-associated molecular patterns, such as advanced glycation-end products and oxidized lipoproteins, is discussed. Finally, a review is made of the pathogenic mechanisms through which the low-grade systemic inflammation contributes to develop insulin resistance, dyslipidaemia, atherogenesis, type 2 diabetes, and hypertension in obese individuals.

CONCLUSIONS

A better understanding of the molecular mechanisms of low-grade systemic inflammation in promoting cardio-metabolic diseases is necessary, in order to further design novel anti-inflammatory therapies that take into consideration clinical data, as well as the circulating levels of cytokines, immune cells, and metabolic damage-associated molecular patterns in each patient.

One week treatment with the IL-1 receptor antagonist anakinra leads to a sustained improvement in insulin sensitivity in insulin resistant patients with type 1 diabetes mellitus

Inflammation associated with obesity is involved in the development of insulin resistance. We hypothesized that anti-inflammatory treatment with the Interleukin-1 receptor antagonist anakinra would improve insulin sensitivity. In an open label proof-of-concept study, we included overweight patients diagnosed with type 1 diabetes with an HbA1c level over 7.5%. Selecting insulin resistant patients with longstanding type 1 diabetes allowed us to study the effects of anakinra on insulin sensitivity. Patients were treated with 100mg anakinra daily for one week. Insulin sensitivity, insulin need and blood glucose profiles were measured before, after one week and after four weeks of follow-up. Fourteen patients completed the study. One week of anakinra treatment led to an improvement of insulin sensitivity, an effect that was sustained for four weeks. Similarly, glucose profiles, HbA1c levels and insulin needs improved. In conclusion, one week of treatment with anakinra improves insulin sensitivity in patients with type 1 diabetes.

Postprandial Dysmetabolism and Oxidative Stress in Type 2 Diabetes: Pathogenetic Mechanisms and Therapeutic Strategies

Postprandial dysmetabolism in type 2 diabetes (T2D) is known to impact the progression and evolution of this complex disease process. However, the underlying pathogenetic mechanisms still require full elucidation to provide guidance for disease prevention and treatment. This review focuses on the marked redox changes and inflammatory stimuli provoked by the spike in blood glucose and lipids in T2D individuals after meals. All the causes of exacerbated postprandial oxidative stress in T2D were analyzed, also considering the consequence of enhanced inflammation on vascular damage. Based on this in-depth analysis, current strategies of prevention and pharmacologic management of T2D were critically reexamined with particular emphasis on their potential redox-related rationale.

Amelioration of mitochondrial dysfunction-induced insulin resistance in differentiated 3T3-L1 adipocytes via inhibition of NF-κB pathways

A growing body of evidence suggests that activation of nuclear factor kappa B (NF-κB) signaling pathways is among the inflammatory mechanism involved in the development of insulin resistance and chronic low-grade inflammation in adipose tissues derived from obese animal and human subjects. Nevertheless, little is known about the roles of NF-κB pathways in regulating mitochondrial function of the adipose tissues. In the present study, we sought to investigate the direct effects of celastrol (potent NF-κB inhibitor) upon mitochondrial dysfunction-induced insulin resistance in 3T3-L1 adipocytes. Celastrol ameliorates mitochondrial dysfunction by altering mitochondrial fusion and fission in adipocytes. The levels of oxidative DNA damage, protein carbonylation and lipid peroxidation were down-regulated. Further, the morphology and quantification of intracellular lipid droplets revealed the decrease of intracellular lipid accumulation with reduced lipolysis. Moreover, massive production of the pro-inflammatory mediators tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were markedly depleted. Insulin-stimulated glucose uptake activity was restored with the enhancement of insulin signaling pathways. This study signified that the treatments modulated towards knockdown of NF-κB transcription factor may counteract these metabolic insults exacerbated in our model of synergy between mitochondrial dysfunction and inflammation. These results demonstrate for the first time that NF-κB inhibition modulates mitochondrial dysfunction induced insulin resistance in 3T3-L1 adipocytes.

Fatty acids and cardiac disease: fuel carrying a message

From the viewpoint of the prevention of cardiovascular disease (CVD) burden, there has been a continuous interest in the detrimental effects of the Western-type high-fat diet for more than half a century. More recently, this general view has been subject to change as epidemiological studies showed that replacing fat by carbohydrate may even be worse and that various polyunsaturated fatty acids (FA) have beneficial rather than detrimental effects on CVD outcome. At the same time, advances in lipid biology have provided insight into the mechanisms by which the different lipid components of the Western diet affect the cardiovascular system. In fact, this still is a rapidly growing field of research and in recent years novel FA derivatives and FA receptors have been discovered. This includes fish-oil derived FA-derivatives with anti-inflammatory properties, the so-called resolvins, and various G-protein-coupled receptors that recognize FA as ligands. In the present review, we will extensively discuss the role of FA and their metabolites on cardiac disease, with special emphasis on the role of the different saturated and polyunsaturated FA and their respective metabolites in cellular signal transduction and the possible implications for the development of cardiac hypertrophy and cardiac failure.

Epigallocatechin gallate improves insulin signaling by decreasing toll-like receptor 4 (TLR4) activity in adipose tissues of high-fat diet rats

SCOPE

In this study, we investigated the beneficial effects and the underlying mechanism of epigallocatechin gallate (EGCG) in adipose tissues of rats fed with a high-fat diet (HFD).

METHODS AND RESULTS

Fasting plasma insulin, epididymal fat coefficient and free fatty acids, homeostasis model assessment-insulin resistance index, and the average glucose infusion rate were determined. EGCG significantly decreased free fatty acids, fasting insulin, homeostasis model assessment-insulin resistance index, and epididymal fat coefficient, and increased glucose infusion rate in HFD group. The levels of toll-like receptor 4, TNF receptor associated factor 6, inhibitor-kappa-B kinase β, p-nuclear factor κB, tumor necrosis factor α, and IL-6 in the EGCG group were all significantly lower than the HFD control group. EGCG also decreased the level of phosphorylated insulin receptor substrate 1 and increased phosphoinositide-3-kinase and glucose transporter isoform 4 in the HFD group. Decreased macrophage infiltration was in EGCG group versus HFD group, and the protein level of CD68 in EGCG group was also significantly lower than that of HFD group.

CONCLUSION

EGCG attenuated inflammation by decreasing the content of macrophages, interfered the toll-like receptor 4 mediated inflammatory response pathway, thus, improving insulin signaling in adipose tissues.

A role for adipocyte-derived lipopolysaccharide-binding protein in inflammation- and obesity-associated adipose tissue dysfunction

AIMS/HYPOTHESIS

Circulating lipopolysaccharide-binding protein (LBP) is an acute-phase reactant known to be increased in obesity. We hypothesised that LBP is produced by adipose tissue (AT) in association with obesity.

METHODS

LBP mRNA and LBP protein levels were analysed in AT from three cross-sectional (n = 210, n = 144 and n = 28) and three longitudinal (n = 8, n = 25, n = 20) human cohorts; in AT from genetically manipulated mice; in isolated adipocytes; and in human and murine cell lines. The effects of a high-fat diet and exposure to lipopolysaccharide (LPS) and peroxisome proliferator-activated receptor (PPAR)γ agonist were explored. Functional in vitro and ex vivo experiments were also performed.

RESULTS

LBP synthesis and release was demonstrated to increase with adipocyte differentiation in human and mouse AT, isolated adipocytes and human and mouse cell lines (Simpson-Golabi-Behmel syndrome [SGBS], human multipotent adipose-derived stem [hMAD] and 3T3-L1 cells). AT LBP expression was robustly associated with inflammatory markers and increased with metabolic deterioration and insulin resistance in two independent cross-sectional human cohorts. AT LBP also increased longitudinally with weight gain and excessive fat accretion in both humans and mice, and decreased with weight loss (in two other independent cohorts), in humans with acquired lipodystrophy, and after ex vivo exposure to PPARγ agonist. Inflammatory agents such as LPS and TNF-α led to increased AT LBP expression in vivo in mice and in vitro, while this effect was prevented in Cd14-knockout mice. Functionally, LBP knockdown using short hairpin (sh)RNA or anti-LBP antibody led to increases in markers of adipogenesis and decreased adipocyte inflammation in human adipocytes.

CONCLUSIONS/INTERPRETATION

Collectively, these findings suggest that LBP might have an essential role in inflammation- and obesity-associated AT dysfunction.

Postprandial interleukin-6 response in elderly with abdominal obesity and metabolic syndrome

OBJECTIVE

The aim of this study is to evaluate the contribution of central obesity to inflammatory responses in the postprandial state in elderly patients with and without metabolic syndrome (MetS).

MATERIAL/METHODS

We evaluated 80 elderly individuals who were distributed into three groups: MetS, abdominal obesity (AbObes) and Control, according to ATPIII criteria. Interleukin-6 (IL-6) serum concentration was measured at 0, 2, 4 and 6 hours after the ingestion of a physiological meal without an overload of fat.

RESULTS

Serum IL-6 increased 6 hours after the meal in all of the groups (P<0.001). Comparing the groups, there was no difference in the area under the curve (AUC) of IL-6 in the postprandial state. There was a correlation between the 6-hour changes in the concentrations of IL-6 and the homeostasis model assessment of insulin resistance (HOMA-IR) (r = 0.25, P<0.05).

CONCLUSION

In this study, differences in abdominal circumference (AC) have not determined a different behavior of IL-6 in the postprandial state, despite the correlation between AC and IL-6. However, we found that, in the elderly, there is a rise in serum IL-6 at 6 hours.

Metabolic endotoxaemia: is it more than just a gut feeling?

PURPOSE OF REVIEW

This article reviews the evidence linking gut bacteria, endotoxin, and its circulating levels with inflammatory induced obesity and metabolic disease (metabolic endotoxaemia).

RECENT FINDINGS

Gut flora analyses have allowed gut microbiota signatures (GMS) to be observed in animal studies of obesity/metabolic disease. In these studies, specific GMS result in a change in obesity and metabolic disease state whereas in humans, analysis remains unclear. Serum studies, examining metabolic endotoxaemia as a biomarker, appear to link long-term cardiovascular disease and type 2 diabetes mellitus (T2DM) through activation of inflammatory pathways. More recent studies note the importance of diet, which shows the dramatic rise in endotoxin following acute or long-term high-fat diet, with the effects exacerbated in T2DM.

SUMMARY

Gut flora appears to act as an important determinant in the pathogenesis of inflammatory induced obesity/T2DM. Endotoxin may act as the systemic insult, impacted by a high-fat diet, which may regulate this effect, combined with an altered GMS. As such, clinical and dietary intervention to affect this process - on the gut flora, the 'leaky' mucosal membrane and endotoxin coupled lipid absorption or removal of circulating endotoxin - could reduce the progression of inflammatory induced metabolic disease.

Lipotoxicity: effects of dietary saturated and transfatty acids

The ingestion of excessive amounts of saturated fatty acids (SFAs) and transfatty acids (TFAs) is considered to be a risk factor for cardiovascular diseases, insulin resistance, dyslipidemia, and obesity. The focus of this paper was to elucidate the influence of dietary SFA and TFA intake on the promotion of lipotoxicity to the liver and cardiovascular, endothelial, and gut microbiota systems, as well as on insulin resistance and endoplasmic reticulum stress. The saturated and transfatty acids favor a proinflammatory state leading to insulin resistance. These fatty acids can be involved in several inflammatory pathways, contributing to disease progression in chronic inflammation, autoimmunity, allergy, cancer, atherosclerosis, hypertension, and heart hypertrophy as well as other metabolic and degenerative diseases. As a consequence, lipotoxicity may occur in several target organs by direct effects, represented by inflammation pathways, and through indirect effects, including an important alteration in the gut microbiota associated with endotoxemia. Interactions between these pathways may perpetuate a feedback process that exacerbates an inflammatory state. The importance of lifestyle modification, including an improved diet, is recommended as a strategy for treatment of these diseases.

Adipokine inflammation and insulin resistance: the role of glucose, lipids and endotoxin

Adipose tissue is an active endocrine organ, and our knowledge of this secretory tissue, in recent years, has led us to completely rethink how our body functions and becomes dysregulated with weight gain. Human adipose tissue appears to act as a multifunctional secretory organ with the capacity to control energy homoeostasis through peripheral and central regulation of energy homoeostasis. It also plays an important role in innate immunity. However, the capability to more than double its original mass to cope with positive energy balance in obesity leads to many pathogenic changes. These changes arise within the adipose tissue as well as inducing secondary detrimental effects on other organs like muscle and liver, including chronic low-grade inflammation mediated by adipocytokines (adipokine inflammation). This inflammation is modulated by dietary factors and nutrients including glucose and lipids, as well as gut bacteria in the form of endotoxin or LPS. The aim of this current review is to consider the impact of nutrients such as glucose and lipids on inflammatory pathways, specifically within adipose tissue. Furthermore, how nutrients such as these can influence adipokine inflammation and consequently insulin resistance directly through their effects on secretion of adipocytokines (TNFα, IL6 and resistin) as well as indirectly through increases in endotoxin is discussed.

Does endotoxaemia contribute to osteoarthritis in obese patients?

OA (osteoarthritis) is a degenerative condition associated with obesity. A number of metabolic explanations have been proposed to explain the association between obesity and OA in non-weight-bearing joints; however, none of these hypotheses have been demonstrated empirically. In the present Hypothesis article, we recognize that obesity is associated with compromised gut mucosa, translocation of microbiota and raised serum LPS (lipopolysaccharide). The consequent activation of the innate immune response leads to increased serum titres of inflammatory mediators in obese patients, with both local and systemic markers of inflammation associated with onset and progression of OA. Furthermore, a number of workers have shown that articular cartilage repair is impaired by a range of inflammatory mediators, both in vitro and in vivo. We propose that metabolic endotoxaemia, caused by impaired gastric mucosa and low-grade chronic inflammation, may contribute to the onset and progression of OA in obese patients. This may account for the association between obesity and OA at non-weight-bearing joints which cannot be explained by biomechanical factors.

High fat intake leads to acute postprandial exposure to circulating endotoxin in type 2 diabetic subjects

OBJECTIVE

To evaluate the changes in circulating endotoxin after a high-saturated fat meal to determine whether these effects depend on metabolic disease state.

RESEARCH DESIGN AND METHODS

Subjects (n = 54) were given a high-fat meal (75 g fat, 5 g carbohydrate, 6 g protein) after an overnight fast (nonobese control [NOC]: age 39.9 ± 11.8 years [mean ± SD], BMI 24.9 ± 3.2 kg/m(2), n = 9; obese: age 43.8 ± 9.5 years, BMI 33.3 ± 2.5 kg/m(2), n = 15; impaired glucose tolerance [IGT]: age 41.7 ± 11.3 years, BMI 32.0 ± 4.5 kg/m(2), n = 12; type 2 diabetic: age 45.4 ± 10.1 years, BMI 30.3 ± 4.5 kg/m(2), n = 18). Blood was collected before (0 h) and after the meal (1-4 h) for analysis.

RESULTS

Baseline endotoxin was significantly higher in the type 2 diabetic and IGT subjects than in NOC subjects, with baseline circulating endotoxin levels 60.6% higher in type 2 diabetic subjects than in NOC subjects (P < 0.05). Ingestion of a high-fat meal led to a significant rise in endotoxin levels in type 2 diabetic, IGT, and obese subjects over the 4-h time period (P < 0.05). These findings also showed that, at 4 h after a meal, type 2 diabetic subjects had higher circulating endotoxin levels (125.4%↑) than NOC subjects (P < 0.05).

CONCLUSIONS

These studies have highlighted that exposure to a high-fat meal elevates circulating endotoxin irrespective of metabolic state, as early as 1 h after a meal. However, this increase is substantial in IGT and type 2 diabetic subjects, suggesting that metabolic endotoxinemia is exacerbated after high fat intake. In conclusion, our data suggest that, in a compromised metabolic state such as type 2 diabetes, a continual snacking routine will cumulatively promote their condition more rapidly than in other individuals because of the greater exposure to endotoxin.