Serum amyloid A: production by human white adipocyte and regulation by obesity and nutrition

Diet-Induced Early Inflammatory Response of Visceral Adipose Tissue in Healthy Male Wistar Rats

The prolonged consumption of a high-fat diet (HFD) leads to abnormal growth of the visceral adipose tissue (VAT), increased macrophage infiltration, and altered secretion of biologically active molecules. This is considered as a precondition for the development of obesity, inflammation, and obesity-related disorders. Therefore, we studied HFD-induced changes in the tissue levels of the inflammatory markers C-reactive protein, serum amyloid-A, and interleukin-4 in healthy male Wistar rats. The animals were first divided at random into two groups subjected to either a standard or a high-fat diet. The initial effect of the diet was evaluated after fourteen weeks. In order to study the diet duration effect, the standard diet was given to twelve animals from the HFD group, while the remaining continued with the HFD for an additional four weeks. Our results showed that the HFD barely affected body mass index, conicity, relative fat mass, and Lee indices, whereas it provoked adipocyte hypertrophy and gradually increased the levels of both the pro- and anti-inflammatory markers. The switch from the high-fat to the standard diet resulted in the comparatively fast restoration of the baseline levels of the studied molecules. Although, the prolonged consumption of an HFD causes adipocyte hypertrophy in healthy male animals, the inflammatory process in VAT is well-coordinated, time-dependent, and reversible.

Serum Versus Fecal Calprotectin Levels in Patients with Severe Obesity Before and 6 Months After Roux-Y-Gastric Bypass: Report of the Prospective Leaky-Gut Study

INTRODUCTION

Obesity is associated with low-grade inflammation, including intestinal inflammation based on fecal or serum calprotectin (FC-SC) measurement. Roux-en-Y gastric bypass (RYGB) improves obesity-related parameters. However, the association between FC-SC levels and postoperative course and the link with metabolic and inflammatory phenotypes before and after RYGB remains unclear.

METHODS

We determined SC levels in 48 patients before (T0) and 6 months after (T6M) RYGB. We then analyzed postoperative changes in FC-SC levels and the relationship with inflammation and metabolic status.

RESULTS

Twenty-three patients (48%) had elevated SC levels (˃2.9 μg/mL) at T0 and T6M. Six of 29 patients (20.7%) had elevated FC concentrations (>50 μg/g) at T0 vs. 16 of 17 patients (94.1%) at T6M (p=0.006). At T0, FC levels correlated with BMI (Rho=0.63; p=0.001) and systemic inflammation (CRP: Rho=0.66, p=0.0006; IL-6: Rho=0.48, p=0.03; haptoglobin: Rho=0.75; p= 0.0006). SC tended to be positively associated with triglyceride levels (Rho=0.34; p=0.08), BMI (Rho=0.34; p=0.08), and inflammatory markers (CRP: Rho=0.33; p=0.09; IL-6: Rho=0.36; p=0.06). FC levels were associated with increased jejunal IL-17+CD8+ T-cell densities (Rho:0.90; p=0.0002). FC and SC were correlated together at T0 (Rho=0.83; p<0.001) but not at T6M. At T6M, SC decreased by 53.6%, whereas FC increased by 79.7%. SC and FC were not associated with any of the variables studied at T6M.

CONCLUSION

FC is a surrogate marker of systemic and intestinal inflammation and adiposity, whereas SC only tends to correlate with systemic inflammation. At 6 months after RYGB, SC-based systemic inflammation decreased, whereas FC-based intestinal inflammation increased. FC and SC levels follow different trajectories and are unrelated to improvements following bariatric surgery.

Serum amyloid A and metabolic disease: evidence for a critical role in chronic inflammatory conditions

Serum amyloid A (SAA) subtypes 1-3 are well-described acute phase reactants that are elevated in acute inflammatory conditions such as infection, tissue injury, and trauma, while SAA4 is constitutively expressed. SAA subtypes also have been implicated as playing roles in chronic metabolic diseases including obesity, diabetes, and cardiovascular disease, and possibly in autoimmune diseases such as systemic lupus erythematosis, rheumatoid arthritis, and inflammatory bowel disease. Distinctions between the expression kinetics of SAA in acute inflammatory responses and chronic disease states suggest the potential for differentiating SAA functions. Although circulating SAA levels can rise up to 1,000-fold during an acute inflammatory event, elevations are more modest (∼5-fold) in chronic metabolic conditions. The majority of acute-phase SAA derives from the liver, while in chronic inflammatory conditions SAA also derives from adipose tissue, the intestine, and elsewhere. In this review, roles for SAA subtypes in chronic metabolic disease states are contrasted to current knowledge about acute phase SAA. Investigations show distinct differences between SAA expression and function in human and animal models of metabolic disease, as well as sexual dimorphism of SAA subtype responses.

The Association of Acute Phase Proteins in Stress and Inflammation-Induced T2D

Acute phase proteins (APPs), such as plasminogen activator inhibitor-1 (PAI-1), serum amyloid A (SAA), and C-reactive protein (CRP), are elevated in type-2 diabetes (T2D) and are routinely used as biomarkers for this disease. These APPs are regulated by the peripheral mediators of stress (i.e., endogenous glucocorticoids (GCs)) and inflammation (i.e., pro-inflammatory cytokines), with both implicated in the development of insulin resistance, the main risk factor for the development of T2D. In this review we propose that APPs, PAI-1, SAA, and CRP, could be the causative rather than only a correlative link between the physiological elements of risk (stress and inflammation) and the development of insulin resistance.

Adipocyte-Derived Serum Amyloid A Promotes Angiotensin II-Induced Abdominal Aortic Aneurysms in Obese C57BL/6J Mice

BACKGROUND

Obesity increases the risk for human abdominal aortic aneurysms (AAAs) and enhances Ang II (angiotensin II)-induced AAA formation in C57BL/6J mice. Obesity is also associated with increases in perivascular fat that expresses proinflammatory markers including SAA (serum amyloid A). We previously reported that deficiency of SAA significantly reduces Ang II-induced inflammation and AAA in hyperlipidemic apoE-deficient mice. In this study. we investigated whether adipose tissue-derived SAA plays a role in Ang II-induced AAA in obese C57BL/6J mice.

METHODS

The development of AAA was compared between male C57BL/6J mice (wild type), C57BL/6J mice lacking SAA1.1, SAA2.1, and SAA3 (TKO); and TKO mice harboring a doxycycline-inducible, adipocyte-specific SAA1.1 transgene (TKO-Tgfat; SAA expressed only in fat). All mice were fed an obesogenic diet and doxycycline to induce SAA transgene expression and infused with Ang II to induce AAA.

RESULTS

In response to Ang II infusion, SAA expression was significantly increased in perivascular fat of obese C57BL/6J mice. Maximal luminal diameters of the abdominal aorta were determined by ultrasound before and after Ang II infusion, which indicated a significant increase in aortic luminal diameters in wild type and TKO-TGfat mice but not in TKO mice. Adipocyte-specific SAA expression was associated with MMP (matrix metalloproteinase) activity and macrophage infiltration in abdominal aortas of Ang II-infused obese mice.

CONCLUSIONS

We demonstrate for the first time that SAA deficiency protects obese C57BL/6J mice from Ang II-induced AAA. SAA expression only in adipocytes is sufficient to cause AAA in obese mice infused with Ang II.

Transcriptome and fatty-acid signatures of adipocyte hypertrophy and its non-invasive MR-based characterization in human adipose tissue

Background

The adipocyte-hypertrophy associated remodeling of fat cell function is considered causal for the development of metabolic disorders. A better understanding of transcriptome and fatty acid (FA) related alterations with adipocyte hypertrophy combined with less-invasive strategies for the detection of the latter can help to increase the prognostic and diagnostic value of adipocyte size and FA composition as markers for metabolic disease.

Methods

To clarify adipocyte-hypertrophy associated transcriptomic alterations, fat cell size was related to RNA-Seq data from white adipose tissue and size-separated adipocytes. The relationship between adipocyte size and adipose tissue FA composition as measured by GC-MS was investigated. MR spectroscopy (MRS) methods for clinical scanning were developed to characterize adipocyte size and FA composition in a fast and non-invasive manner.

Findings

With enlarged adipocyte size, substantial transcriptomic alterations of genes involved in mitochondrial function and FA metabolism were observed. Investigations of these two mechanisms revealed a reciprocal relationship between adipocyte size and estimated thermogenic adipocyte content as well as depot-specific correlations of adipocyte size and FA composition. MRS on a clinical scanner was suitable for the in-parallel assessment of adipose morphology and FA composition.

Interpretation

The current study provides a comprehensive overview of the adipocyte-hypertrophy associated transcriptomic and FA landscape in both subcutaneous and visceral adipose tissue. MRS represents a promising technique to translate the observed mechanistic, structural and functional changes in WAT with adipocyte hypertrophy into a clinical context for an improved phenotyping of WAT in the context of metabolic diseases.

Funding

Competence network for obesity (FKZ 42201GI1128), ERC (No 677661, ProFatMRI; No 875488, FatVirtualBiopsy), Else Kröner-Fresenius-Foundation.

Serum Amyloid A is not obligatory for high-fat, high-sucrose, cholesterol-fed diet-induced obesity and its metabolic and inflammatory complications

Several studies in the past have reported positive correlations between circulating Serum amyloid A (SAA) levels and obesity. However, based on limited number of studies involving appropriate mouse models, the role of SAA in the development of obesity and obesity-related metabolic consequences has not been established. Accordingly, herein, we have examined the role of SAA in the development of obesity and its associated metabolic complications in vivo using mice deficient for all three inducible forms of SAA: SAA1.1, SAA2.1 and SAA3 (TKO). Male and female mice were rendered obese by feeding a high fat, high sucrose diet with added cholesterol (HFHSC) and control mice were fed rodent chow diet. Here, we show that the deletion of SAA does not affect diet-induced obesity, hepatic lipid metabolism or adipose tissue inflammation. However, there was a modest effect on glucose metabolism. The results of this study confirm previous findings that SAA levels are elevated in adipose tissues as well as in the circulation in diet-induced obese mice. However, the three acute phase SAAs do not play a causative role in the development of obesity or obesity-associated adipose tissue inflammation and dyslipidemia.

Role of Serum Amyloid A in Abdominal Aortic Aneurysm and Related Cardiovascular Diseases

Epidemiological data positively correlate plasma serum amyloid A (SAA) levels with cardiovascular disease severity and mortality. Studies by several investigators have indicated a causal role for SAA in the development of atherosclerosis in animal models. Suppression of SAA attenuates the development of angiotensin II (AngII)-induced abdominal aortic aneurysm (AAA) formation in mice. Thus, SAA is not just a marker for cardiovascular disease (CVD) development, but it is a key player. However, to consider SAA as a therapeutic target for these diseases, the pathway leading to its involvement needs to be understood. This review provides a brief description of the pathobiological significance of this enigmatic molecule. The purpose of this review is to summarize the data relevant to its role in the development of CVD, the pitfalls in SAA research, and unanswered questions in the field.

Inhibitory Effects of Six Types of Tea on Aging and High-Fat Diet-Related Amyloid Formation Activities

Aging and lipid metabolism disorders promote the formation and accumulation of amyloid with β-sheet structure, closely related to cardiovascular disease, senile dementia, type 2 diabetes, and other senile degenerative diseases. In this study, five representative teas were selected from each of the six types of tea, and a total of 30 teas were selected to evaluate the inhibitory activities on the formation of aging-related amyloid in vitro. The results showed that the 30 teas had a significant inhibitory effect on the formation activity on aging-related amyloid at the protein level in vitro. Although the content of catechins is relatively low, black tea and dark tea still have significant antioxidant activity and inhibit the formation of amyloid. A high-fat diet established the model of lipid metabolism disorder in premature aging SAMP8 mice, and these mice were gavaged different tea water extracts. The results showed that different tea types have a significant inhibitory effect on the formation of β-amyloid and Aβ42 mediated by age-related lipid metabolism disorders, and the in vivo activity of fully fermented teas was better than that of green tea. The action mechanism was related to antioxidation, anti-inflammatory, and improving lipid metabolism.

Serum Amyloid A Proteins and Their Impact on Metastasis and Immune Biology in Cancer

Simple Summary

The liver responds to systemic inflammation and injury in a coordinated manner, called the acute phase response. While this normal physiological response aims to restore homeostasis, malignant transformation coopts this biology to increase the risk for metastasis, immune evasion, and therapeutic resistance. In this Review, we discuss the importance of acute phase response proteins in regulating cancer biology and treatment efficacy. We also consider potential strategies to intervene on acute phase biology as an approach to improve outcomes in cancer.

Abstract

Cancer triggers the systemic release of inflammatory molecules that support cancer cell metastasis and immune evasion. Notably, this biology shows striking similarity to an acute phase response that is coordinated by the liver. Consistent with this, a role for the liver in defining cancer biology is becoming increasingly appreciated. Understanding the mechanisms that link acute phase biology to metastasis and immune evasion in cancer may reveal vulnerable pathways and novel therapeutic targets. Herein, we discuss a link between acute phase biology and cancer with a focus on serum amyloid A proteins and their involvement in regulating the metastatic cascade and cancer immunobiology.

Sexually Dimorphic Relationships Among Saa3 (Serum Amyloid A3), Inflammation, and Cholesterol Metabolism Modulate Atherosclerosis in Mice

[Figure: see text].

Xanthohumol ameliorates Diet-Induced Liver Dysfunction via Farnesoid X Receptor-Dependent and Independent Signaling

The farnesoid X receptor (FXR) plays a critical role in the regulation of lipid and bile acid (BA) homeostasis. Hepatic FXR loss results in lipid and BA accumulation, and progression from hepatic steatosis to nonalcoholic steatohepatitis (NASH). This study aimed to evaluate the effects of xanthohumol (XN), a hop-derived compound mitigating metabolic syndrome, on liver damage induced by diet and FXR deficiency in mice. Wild-type (WT) and liver-specific FXR-null mice (FXR^Liver−/−) were fed a high-fat diet (HFD) containing XN or the vehicle formation followed by histological characterization, lipid, BA and gene profiling. HFD supplemented with XN resulted in amelioration of hepatic steatosis and decreased BA concentrations in FXR^Liver−/− mice, the effect being stronger in male mice. XN induced the constitutive androstane receptor (CAR), pregnane X receptor (PXR) and glucocorticoid receptor (GR) gene expression in the liver of FXR^Liver−/− mice. These findings suggest that activation of BA detoxification pathways represents the predominant mechanism for controlling hydrophobic BA concentrations in FXR^Liver−/− mice. Collectively, these data indicated sex-dependent relationship between FXR, lipids and BAs, and suggest that XN ameliorates HFD-induced liver dysfunction via FXR-dependent and independent signaling.

Bariatric surgery improves clinical outcomes and adiposity biomarkers but not inflammatory cytokines SAA and MCP-1 after a six-month follow-up

Obesity is a global health problem and is associated with a chronic low-grade inflammatory state. Surgical obesity treatment is being increasingly common due to its efficacy. From this, we evaluate the metabolic state improvement and inflammation remission in patients with obesity undergoing bariatric surgery. Methods: The clinical data and serum levels of leptin and adiponectin were assessed in patients with obesity before and one, three and six months after bariatric surgery. Also, serum amyloid A (SAA), monocyte chemoattractant protein-1 (MCP-1) levels were measured during the follow-up surgery and compared with a lean group of individuals. Results: Weight loss decreased body mass index (BMI), comorbidities percentage, drugs use and leptin levels. Adiponectin levels increased after surgery. SAA and MCP-1 showed no difference after surgery, but a trend decrease for MCP-1 and a significant decrease was observed when the patients with obesity were compared to the lean participants. Conclusion: Bariatric surgery alters metabolic status improving obesity-related comorbidities and the adiposity biomarkers leptin and adiponectin, but not inflammatory cytokines SAA and MCP-1.

Association of Adipose Tissue and Adipokines with Development of Obesity-Induced Liver Cancer

Obesity is rapidly dispersing all around the world and is closely associated with a high risk of metabolic diseases such as insulin resistance, dyslipidemia, and nonalcoholic fatty liver disease (NAFLD), leading to carcinogenesis, especially hepatocellular carcinoma (HCC). It results from an imbalance between food intake and energy expenditure, leading to an excessive accumulation of adipose tissue (AT). Adipocytes play a substantial role in the tumor microenvironment through the secretion of several adipokines, affecting cancer progression, metastasis, and chemoresistance via diverse signaling pathways. AT is considered an endocrine organ owing to its ability to secrete adipokines, such as leptin, adiponectin, resistin, and a plethora of inflammatory cytokines, which modulate insulin sensitivity and trigger chronic low-grade inflammation in different organs. Even though the precise mechanisms are still unfolding, it is now established that the dysregulated secretion of adipokines by AT contributes to the development of obesity-related metabolic disorders. This review focuses on several obesity-associated adipokines and their impact on obesity-related metabolic diseases, subsequent metabolic complications, and progression to HCC, as well as their role as potential therapeutic targets. The field is rapidly developing, and further research is still required to fully understand the underlying mechanisms for the metabolic actions of adipokines and their role in obesity-associated HCC.

Effects of equine metabolic syndrome on inflammation and acute-phase markers in horses

Obesity and metabolic disorders are associated with systemic low-grade chronic inflammation, both in humans and animals. The aim of the study is to assess the effects of obesity and hyperinsulinemia on individual components of the acute-phase reaction in equine metabolic syndrome (EMS) horses. Eight mixed-breed EMS and six control, age-matched horses of both sexes were included in the study. Animals were classified as EMS or control based on the assessment of BCS, cresty neck score, and basal insulin >50 μU/mL and/or insulin responses to the oral sugar test (OST) >60 μU/mL. Peripheral venous blood was collected. The expression of proinflammatory cytokines, the concentration of circulating cytokines, and acute-phase proteins (serum amyloid A, C-reactive protein, haptoglobin, activin A, and procalcitonin) were measured. The data were analyzed using the Mann-Whitney test, whereas correlations were examined using Spearman's correlation coefficient. The tests were statistically significant if P ≤ 0.05. There were no differences in cytokine gene expression, circulating cytokine concentrations, or concentrations of acute-phase proteins between the EMS and the control groups. There was a strong correlation between the basal concentration of insulin and the serum concentrations of IL-6 (r = 0.71, P < 0.05). Activin A was positively correlated with post-OST insulin concentrations (r = 0.707, P = 0.05), indicating that this marker of inflammation could warrant further investigation in horses with EMS.

Presence of serum amyloid A3 in mouse plasma is dependent on the nature and extent of the inflammatory stimulus

Serum amyloid A3 (Saa3) derives mainly from extrahepatic tissue and is not detected in plasma from moderately inflamed obese mice. In contrast, it is present in plasma from mice acutely inflamed by injection of high dose of lipopolysaccharide (LPS). To reconcile these differences, we evaluated whether different acute inflammatory stimuli could affect the presence of Saa3 in plasma. Saa3 appeared dose dependently in plasma after LPS injection. In contrast, only very low levels were detected after sterile inflammation with silver nitrate despite levels of Saa1 and Saa2 being comparable to high dose LPS. Saa3 was not detected in plasma following casein administration. Although most Saa3 was found in HDL, a small amount was not lipoprotein associated. Gene expression and proteomic analysis of liver and adipose tissue suggested that a major source of Saa3 in plasma after injection of LPS was adipose tissue rather than liver. We conclude that Saa3 only appears in plasma after induction of acute inflammation by some but not all inflammatory stimuli. These findings are consistent with the observation that Saa3 is not detectable in plasma in more moderate chronic inflammatory states such as obesity.

Altered HDL metabolism in metabolic disorders: insights into the therapeutic potential of HDL

Metabolic disorders are associated with an increased risk of cardiovascular disease (CVD), and are commonly characterized by a low plasma level of high-density lipoprotein cholesterol (HDL-C). Although cholesterol lowering medications reduce CVD risk in these patients, they often remain at increased risk of CVD. Therapeutic strategies that raise HDL-C levels and improve HDL function are a potential treatment option for reducing residual CVD risk in these individuals. Over the past decade, understanding of the metabolism and cardioprotective functions of HDLs has improved, with preclinical and clinical studies both indicating that the ability of HDLs to mediate reverse cholesterol transport, inhibit inflammation and reduce oxidation is impaired in metabolic disorders. These cardioprotective effects of HDLs are supported by the outcomes of epidemiological, cell and animal studies, but have not been confirmed in several recent clinical outcome trials of HDL-raising agents. Recent studies suggest that HDL function may be clinically more important than plasma levels of HDL-C. However, at least some of the cardioprotective functions of HDLs are lost in acute coronary syndrome and stable coronary artery disease patients. HDL dysfunction is also associated with metabolic abnormalities. This review is concerned with the impact of metabolic abnormalities, including dyslipidemia, obesity and Type 2 diabetes, on the metabolism and cardioprotective functions of HDLs.

Adipose Tissue Distribution, Inflammation and Its Metabolic Consequences, Including Diabetes and Cardiovascular Disease

Adipose tissue plays essential roles in maintaining lipid and glucose homeostasis. To date several types of adipose tissue have been identified, namely white, brown, and beige, that reside in various specific anatomical locations throughout the body. The cellular composition, secretome, and location of these adipose depots define their function in health and metabolic disease. In obesity, adipose tissue becomes dysfunctional, promoting a pro-inflammatory, hyperlipidemic and insulin resistant environment that contributes to type 2 diabetes mellitus (T2DM). Concurrently, similar features that result from adipose tissue dysfunction also promote cardiovascular disease (CVD) by mechanisms that can be augmented by T2DM. The mechanisms by which dysfunctional adipose tissue simultaneously promote T2DM and CVD, focusing on adipose tissue depot-specific adipokines, inflammatory profiles, and metabolism, will be the focus of this review. The impact that various T2DM and CVD treatment strategies have on adipose tissue function and body weight also will be discussed.

Proteomic Markers of Non-functional Overreaching During the Race Across America (RAAM): A Case Study

In a previous study, proteomics procedures identified blood proteins as potential overreaching and overtraining biomarkers, and a targeted proteomics panel of 21 proteins was developed.

From Table to Stable: A Comparative Review of Selected Aspects of Human and Equine Metabolic Syndrome

Obesity data in people and companion animals are depicting a future of increasing morbidity, cost for society, and significant health and welfare concerns. Between 25 and 50% of cats, dogs, and horses in developed countries are overweight or obese, which mirrors the situation in humans. Equine metabolic syndrome (EMS) was named after human metabolic syndrome (MetS), which has about 30 years of lead in research efforts. Even though the complications of the two syndromes seem to grossly differ (cardiac vs. laminitis risk), a number of similar disease mechanisms are worthy of investigation. Since the first EMS consensus statement by the American College of Veterinary Internal Medicine in 2010, numerous studies have confirmed the link between insulin dysregulation and laminitis, even though the mechanisms are not fully understood. After the discovery of the role of adipokines in MetS, evidence about inflammatory mechanisms related to adiposity in rodent models, companion animals, horses, and humans is constantly increasing. Oxidative and dicarbonyl stress have been correlated with insulin dysregulation, obesity, and recently with laminitis. Vascular actions of insulin through nitric oxide, endothelin-1, and other mechanisms are being studied in horses and can provide a better understanding of laminitis pathophysiology. More research is needed on neuropathic mechanisms in insulin-dysregulated horses, which could be important in the pathogenesis of laminitis and laminitic pain. Human literature can provide viable material for novel studies in areas that have received limited attention, in addition to being valuable information for clients about the consequences of unhealthy management of their horses.

White Adipose Tissue Response of Obese Mice to Ambient Oxygen Restriction at Thermoneutrality: Response Markers Identified, but no WAT Inflammation

Obesity is associated with white adipose tissue (WAT) hypoxia and inflammation. We aimed to test whether mild environmental oxygen restriction (OxR, 13% O₂), imposing tissue hypoxia, triggers WAT inflammation in obese mice. Thirteen weeks diet-induced obese male adult C57BL/6JOlaHsd mice housed at thermoneutrality were exposed for five days to OxR versus normoxia. WAT and blood were isolated and used for analysis of metabolites and adipokines, WAT histology and macrophage staining, and WAT transcriptomics. OxR increased circulating levels of haemoglobin and haematocrit as well as hypoxia responsive transcripts in WAT and decreased blood glucose, indicating systemic and tissue hypoxia. WAT aconitase activity was inhibited. Macrophage infiltration as marker for WAT inflammation tended to be decreased, which was supported by down regulation of inflammatory genes S100a8, Ccl8, Clec9a, Saa3, Mgst2, and Saa1. Other down regulated processes include cytoskeleton remodelling and metabolism, while response to hypoxia appeared most prominently up regulated. The adipokines coiled-coil domain containing 3 (CCDC3) and adiponectin, as well as the putative WAT hormone cholecystokinin (CCK), were reduced by OxR on transcript (Cck, Ccdc3) and/or serum protein level (adiponectin, CCDC3). Conclusively, our data demonstrate that also in obese mice OxR does not trigger WAT inflammation. However, OxR does evoke a metabolic response in WAT, with CCDC3 and adiponectin as potential markers for systemic or WAT hypoxia.

Acute phase reactant serum amyloid A in inflammation and other diseases

Acute-phase reactant serum amyloid A (A-SAA) plays an important role in acute and chronic inflammation and is used in clinical laboratories as an indicator of inflammation. Although both A-SAA and C-reactive protein (CRP) are acute-phase proteins, the detection of A-SAA is more conclusive than the detection of CRP in patients with viral infections, severe acute pancreatitis, and rejection reactions to kidney transplants. A-SAA has greater clinical diagnostic value in patients who are immunosuppressed, patients with cystic fibrosis who are treated with corticoids, and preterm infants with late-onset sepsis. Nevertheless, for the assessment of the inflammation status and identification of viral infection in other pathologies, such as bacterial infections, the combinatorial use of A-SAA and other acute-phase proteins (APPs), such as CRP and procalcitonin (PCT), can provide more information and sensitivity than the use of any of these proteins alone, and the information generated is important in guiding antibiotic therapy. In addition, A-SAA-associated diseases and the diagnostic value of A-SAA are discussed. However, the relationship between different A-SAA isotypes and their human diseases are mostly derived from research laboratories with limited clinical samples. Thus, further clinical evaluations are necessary to confirm the clinical significance of each A-SAA isotype. Furthermore, the currently available A-SAA assays are based on polyclonal antibodies, which lack isotype specificity and are associated with many inflammatory diseases. Therefore, these assays are usually used in combination with other biomarkers in the clinic.

AA amyloidosis associated with morbid obesity (clinical case)

We present the case of a 45-year-old woman who was hospitalized due to severe macrocytic anemia and renal failure. The patient presented a morbid obesity. The immunological study showed anti-ENA anti-SSA (Ro52) positive, with negative antinuclear antibodies. Also in the proteinogram (serum immunofixation) the presence of monoclonal bands IgG lambda and IgG kappa, monoclonal component 7.2% (4.68g/L), with elevation of free light chains (kappa 95.94mg/L (3.3-19.4), evidenced, lambda 145.17mg/L (5.71-26.3)). The bone marrow study showed an infiltration of 5% of plasma cells and positive for AA amyloid. Finally, a percutaneous renal biopsy was performed, which again showed amyloid infiltration. In the genetic study, 2 mutations of the family Mediterranean fever gene (MEFV) have been identified. Secondary AA amyloidosis has been described associated with obesity, in addition to a percentage of cases of unknown etiology.

Serum Amyloid P and Endocrine Markers in a Cohort of Obese Children

OBJECTIVES

Obesity in children can lead to morbidity and mortality due to metabolic and inflammatory comorbidities.

AIMS

The objective of the study was to investigate the alterations in acute inflammatory markers, serum amyloid P (SAP) and cortisol, and endocrine markers, leptin and insulin, in obese children.

MATERIALS AND METHODS

Serum leptin, insulin, cortisol, and amyloid P concentrations were measured in obese (BMI percentile >85, n = 17) and nonobese (BMI percentile < 75, n = 20) children using ELISA and Bio-Plex Bead-based assay.

STATISTICAL ANALYSIS USED

Serum concentrations of analytes were compared between normal and obese groups using 2-tailed student's t-test.

RESULTS

Mean leptin, insulin, and SAP serum concentrations were significantly higher in obese children as compared to the controls (97.19 vs. 4.06, P < 0.05; 21.31 vs 3.56, P < 0.05; 46.77 vs. 17.89, P < 0.05; respectively). No difference was found in mean serum cortisol levels of the two groups. However, cortisol values were higher in obese subjects compared to the control group (7.89 vs 6.30, P = 0.15). Leptin corelated with insulin (r = 0.42, P = 0.043) and cortisol (r = 0.48, P = 0.025) levels in the obese group. Furthermore, leptin, insulin, and SAP levels were corelated with BMI (r = 0.80, P < 0.000; r = 0.67, P = 0.015, respectively) and body weight (r = 0.52, P = 0.01; r = 0.52, P = 0.002; r = 0.54, P = 0.01, respectively) in the obese group but did not demonstrate a significant relationship in the nonobese group.

CONCLUSION

Elevated SAP levels and increase in leptin and insulin indicated a preeminent disposition of morbidly obese children to the development of low-grade inflammation and metabolic syndrome.

Type 2 diabetes - An autoinflammatory disease driven by metabolic stress

Type 2 diabetes has traditionally been viewed as a metabolic disorder characterised by chronic high glucose levels, insulin resistance, and declining insulin secretion from the pancreas. Modern lifestyle, with abundant nutrient supply and reduced physical activity, has resulted in dramatic increases in the rates of obesity-associated disease conditions, including diabetes. The associated excess of nutrients induces a state of systemic low-grade chronic inflammation that results from production and secretion of inflammatory mediators from the expanded pool of activated adipocytes. Here, we review the mechanisms by which obesity induces adipose tissue dysregulation, detailing the roles of adipose tissue secreted factors and their action upon other cells and tissues central to glucose homeostasis and type 2 diabetes. Furthermore, given the emerging importance of adipokines, cytokines and chemokines in disease progression, we suggest that type 2 diabetes should now be viewed as an autoinflammatory disease, albeit one that is driven by metabolic dysregulation.

An Overview of Novel Dietary Supplements and Food Ingredients in Patients with Metabolic Syndrome and Non-Alcoholic Fatty Liver Disease

Metabolic syndrome (MetS) is characterized by interconnected factors related to metabolic disturbances, and is directly related to the occurrence of some diseases such as cardiovascular diseases and type 2 diabetes. MetS is described as one or both of insulin resistance and visceral adiposity, considered the initial causes of abnormalities that include hyperglycemia, elevated blood pressure, dyslipidemia, elevated inflammatory markers, and prothrombotic state, as well as polycystic ovarian syndrome in women. Other than in MetS, visceral adiposity and the pro-inflammatory state are also key in the development of non-alcoholic fatty liver disease (NAFLD), which is the most prevalent chronic liver disease in modern society. Both MetS and NAFLD are related to diet and lifestyle, and their treatment may be influenced by dietary pattern changes and the use of certain dietary supplements. This study aimed to review the role of food ingredients and supplements in the management of MetS and NAFLD specifically in human clinical trials. Moreover, bioactive compounds and polyunsaturated fatty acids (PUFAs) may be used as strategies for preventing the onset of and treatment of metabolic disorders, such as MetS and NAFLD, improving the inflammatory state and other comorbidities, such as obesity, dyslipidemias, and cardiovascular diseases (CVD).

Association between the circulating leptin levels and the biomarkers of oxidative stress and inflammation among Iranian overweight and obese adults

Background: Oxidative stress in obese people is an important pathogenic mechanism of an obesity-associated metabolic syndrome. We evaluated the association between circulating leptin levels with biomarkers of oxidative stress in overweight and obese participants.

Methods: This study was performed on 189 overweight and obese people aged 18-60 years old. Serum leptin, superoxide dismutase (SOD), high-sensitivity C-reactive protein (hs-CRP), homocysteine (Hcy), thiobarbituric acid reactive substances (TBARS) and amyloid A (SAA) concentrations were measured. Pearson correlation and multiple linear regressions were used to assess the relationships.

Results: We found that among the biomarkers of oxidative stress and inflammation in participants, serum hs-CRP and SAA were positively correlated with BMI (β=0.003, P<0.001 and β=7.83, P<0.001, respectively). This relationship remained significant even after controlling other oxidative stress and inflammatory indicators (β=0.003, p<0.001 for hs-CRP), but this association disappeared for SAA. In addition, serum hs-CRP was positively correlated with leptin (β=0.001, p=0.003). Regression analysis showed that there was no association between serum Hcy, SAA, TBARS and SOD with serum leptin concentrations

Conclusion: Overall, the current study demonstrated that serum hs-CRP and SAA levels were independently correlated with BMI. Furthermore, serum hs-CRP was positively correlated with leptin. Focusing on such strategies may lead to promises for alleviating obesity and its co-morbidities.

Current and future therapies for addressing the effects of inflammation on HDL cholesterol metabolism

Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide. Inflammatory processes arising from metabolic abnormalities are known to precipitate the development of CVD. Several metabolic and inflammatory markers have been proposed for predicting the progression of CVD, including high density lipoprotein cholesterol (HDL-C). For ~50 years, HDL-C has been considered as the atheroprotective 'good' cholesterol because of its strong inverse association with the progression of CVD. Thus, interventions to increase the concentration of HDL-C have been successfully tested in animals; however, clinical trials were unable to confirm the cardiovascular benefits of pharmaceutical interventions aimed at increasing HDL-C levels. Based on these data, the significance of HDL-C in the prevention of CVD has been called into question. Fundamental in vitro and animal studies suggest that HDL-C functionality, rather than HDL-C concentration, is important for the CVD-preventive qualities of HDL-C. Our current review of the literature positively demonstrates the negative impact of systemic and tissue (i.e. adipose tissue) inflammation in the healthy metabolism and function of HDL-C. Our survey indicates that HDL-C may be a good marker of adipose tissue health, independently of its atheroprotective associations. We summarize the current findings on the use of anti-inflammatory drugs to either prevent HDL-C clearance or improve the function and production of HDL-C particles. It is evident that the therapeutic agents currently available may not provide the optimal strategy for altering HDL-C metabolism and function, and thus, further research is required to supplement this mechanistic approach for preventing the progression of CVD.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

A human stool-derived Bilophila wadsworthia strain caused systemic inflammation in specific-pathogen-free mice

BACKGROUND

Bilophila wadsworthia is a major member of sulfidogenic bacteria in human gut, it was originally recovered from different clinical specimens of intra-abdominal infections and recently was reported potentially linked to different chronic metabolic disorders. However, there is still insufficient understanding on its detailed function and mechanism to date.

METHODS

A B. wadsworthia strain was isolated from fresh feces of a latent autoimmune diabetes in adults patient and we investigated its pathogenicity by oral administration to specific-pathogen-free mice. Tissue samples and serum were collected after sacrifice. Stool samples were collected at different time points to profile the gut microbiota.

RESULTS

Bilophila wadsworthia infection resulted in the reduction of body weight and fat mass, apparent hepatosplenomegaly and elevated serum inflammatory factors, including serum amyloid A and interleukin-6, while without significant change of the overall gut microbiota structure.

CONCLUSIONS

These results demonstrated that higher amount of B. wadsworthia caused systemic inflammatory response in SPF mice, which adds new evidence to the pathogenicity of this bacterium and implied its potential role to the chronic inflammation related metabolic diseases like diabetes.

T Cell Populations and Functions Are Altered in Human Obesity and Type 2 Diabetes

PURPOSE OF THE REVIEW

Obesity and type 2 diabetes (T2D) are considered chronic inflammatory diseases. While early publications have reported the implication of innate immune cells such as macrophages to promote systemic inflammation and metabolic dysfunctions, recent publications underline the alterations of the T cell compartment in human obesity and type 2 diabetes. These recent findings are the focus of this review.

RECENT FINDINGS

In humans, obesity and T2D induce the expansion of proinflammatory T cells such as CD4 Th1, Th17, and CD8 populations, whereas innate T cells such as MAIT and iNKT cells are decreased. These alterations reflect a loss of total T cell homeostasis that may contribute to tissue and systemic inflammation. Whether these changes are adaptive to nutritional variations and/or contribute to the progression of metabolic diseases remains to be clarified. T cell phenotyping may improve obese and/or T2D patient stratification with therapeutic and prognostic implications.

Involvement of the leptin-adiponectin axis in inflammation and oxidative stress in the metabolic syndrome

The aim of the present work was to study whether the leptin-adiponectin axis may have a pathophysiological role in the increased systemic inflammation and oxidative stress observed in patients with the metabolic syndrome (MS). Leptin, adiponectin, and markers of inflammation and oxidative stress were measured in a sample of 140 Caucasian subjects (74 males/66 females), aged 28-82 years, 60 with and 80 without the MS. Total concentrations of adiponectin as well as its multimeric forms HMW, MMW and LMW were significantly lower in individuals with the MS. The ratio adiponectin/leptin, a marker of dysfunctional adipose tissue, was dramatically decreased in the MS group. Systemic oxidative stress, as evidenced by levels of thiobarbituric acid reactive substances (TBARS), as well as markers of inflammation such as serum amyloid A (SAA), C-reactive protein (CRP) and osteopontin were significantly increased in subjects with the MS. Total adiponectin concentrations were negatively correlated with levels of TBARS and CRP levels. Furthermore, the ratio adiponectin/leptin was negatively correlated with SAA concentrations as well as with CRP levels. We concluded that a dysfunctional adipose tissue as suggested by a low adiponectin/leptin ratio may contribute to the increased oxidative stress and inflammation, hallmarks of the MS.

Microglia activation due to obesity programs metabolic failure leading to type two diabetes

Obesity is an energy metabolism disorder that increases susceptibility to the development of metabolic diseases. Recently, it has been described that obese subjects have a phenotype of chronic inflammation in organs that are metabolically relevant for glucose homeostasis and energy. Altered expression of immune system molecules such as interleukins IL-1, IL-6, IL-18, tumor necrosis factor alpha (TNF-α), serum amyloid A (SAA), and plasminogen activator inhibitor-1 (PAI-1), among others, has been associated with the development of chronic inflammation in obesity. Chronic inflammation modulates the development of metabolic-related comorbidities like metabolic syndrome (insulin resistance, glucose tolerance, hypertension and hyperlipidemia). Recent evidence suggests that microglia activation in the central nervous system (CNS) is a priority in the deregulation of energy homeostasis and promotes increased glucose levels. This review will cover the most significant advances that explore the molecular signals during microglia activation and inflammatory stage in the brain in the context of obesity, and its influence on the development of metabolic syndrome and type two diabetes.

Mucosal Interactions between Genetics, Diet, and Microbiome in Inflammatory Bowel Disease

Numerous reviews have discussed gut microbiota composition changes during inflammatory bowel diseases (IBD), particularly Crohn’s disease (CD). However, most studies address the observed effects by focusing on studying the univariate connection between disease and dietary-induced alterations to gut microbiota composition. The possibility that these effects may reflect a number of other interconnected (i.e., pantropic) mechanisms, activated in parallel, particularly concerning various bacterial metabolites, is in the process of being elucidated. Progress seems, however, hampered by various difficult-to-study factors interacting at the mucosal level. Here, we highlight some of such factors that merit consideration, namely: (1) the contribution of host genetics and diet in altering gut microbiome, and in turn, the crosstalk among secondary metabolic pathways; (2) the interdependence between the amount of dietary fat, the fatty acid composition, the effects of timing and route of administration on gut microbiota community, and the impact of microbiota-derived fatty acids; (3) the effect of diet on bile acid composition, and the modulator role of bile acids on the gut microbiota; (4) the impact of endogenous and exogenous intestinal micronutrients and metabolites; and (5) the need to consider food associated toxins and chemicals, which can introduce confounding immune modulating elements (e.g., antioxidant and phytochemicals in oils and proteins). These concepts, which are not mutually exclusive, are herein illustrated paying special emphasis on physiologically inter-related processes.

Roles of Reactive Oxygen Species on Insulin Resistance in Adipose Tissue

Obesity resulting from the delivery of an excess amount of energy to adipose tissue from glucose or free fatty acids is associated with insulin resistance and adipose tissue inflammation. Reactive oxygen species (ROS) have been implicated as contributors to both the onset and the progression of insulin resistance. ROS can be generated by overloading the mitochondrial oxidative phosphorylation system, and also by nicotinamide adenine dinucleotide phosphate oxidases (NOX) produced by either adipocytes, which only produce NOX4, or by macrophages, which produce mainly NOX2. The source of the ROS might differ in the early, intermediate and late stages of obesity, switching from NOX4-dependence in the early phases to NOX2-dependence, in the intermediate phase, and transiting to mitochondria-dependence later in the time course of obesity. Thus, depending on the stage of obesity, ROS can be generated by three distinct mechanisms: i.e., NOX4, NOX2, and mitochondria. In this review, we will discuss whether NOX4-, NOX2-, and/or mitochondria-derived ROS is/are causal in the onset of adipocyte insulin resistance as obesity progresses. Moreover, we will review the pathophysiological roles of NOX4, NOX2, and mitochondria-derived ROS on adipose tissue inflammation.

Serum amyloid A1 levels and amyloid deposition following a high-fat diet challenge in transgenic mice overexpressing hepatic serum amyloid A1

Serum amyloid A (SAA) is an acute-phase response protein in the liver, and SAA1 is the major precursor protein involved in amyloid A amyloidosis. This amyloidosis has been reported as a complication in chronic inflammatory conditions such as arthritis, lupus, and Crohn's disease. Obesity is also associated with chronic, low-grade inflammation and sustained, elevated levels of SAA1. However, the contribution of elevated circulating SAA1 to metabolic disturbances and their complications is unclear. Furthermore, in several recent studies of transgenic (TG) mice overexpressing SAA1 that were fed a high-fat diet (HFD) for a relatively short period, no relationship was found between SAA1 up-regulation and metabolic disturbances. Therefore, we generated TG mice overexpressing SAA1 in the liver, challenged these mice with an HFD, and investigated the influence of elevated SAA1 levels. Sustained, elevated levels of SAA1 were correlated with metabolic parameters and local cytokine expression in the liver following 16 weeks on the HFD. Moreover, prolonged consumption (52 weeks) of the HFD was associated with impaired glucose tolerance and elevated SAA1 levels and resulted in systemic SAA1-derived amyloid deposition in the kidney, liver, and spleen of TG mice. Thus, we concluded that elevated SAA1 levels under long-term HFD exposure result in extensive SAA1-derived amyloid deposits, which may contribute to the complications associated with HFD-induced obesity and metabolic disorders.

Obesity-induced chronic inflammation in high fat diet challenged C57BL/6J mice is associated with acceleration of age-dependent renal amyloidosis

Obesity-induced inflammation presumably accelerates the development of chronic kidney diseases. However, little is known about the sequence of these inflammatory events and their contribution to renal pathology. We investigated the effects of obesity on the evolution of age-dependent renal complications in mice in conjunction with the development of renal and systemic low-grade inflammation (LGI). C57BL/6J mice susceptible to develop age-dependent sclerotic pathologies with amyloid features in the kidney, were fed low (10% lard) or high-fat diets (45% lard) for 24, 40 and 52 weeks. HFD-feeding induced overt adiposity, altered lipid and insulin homeostasis, increased systemic LGI and adipokine release. HFD-feeding also caused renal upregulation of pro-inflammatory genes, infiltrating macrophages, collagen I protein, increased urinary albumin and NGAL levels. HFD-feeding severely aggravated age-dependent structural changes in the kidney. Remarkably, enhanced amyloid deposition rather than sclerosis was observed. The degree of amyloidosis correlated significantly with body weight. Amyloid deposits stained positive for serum amyloid A (SAA) whose plasma levels were chronically elevated in HFD mice. Our data indicate obesity-induced chronic inflammation as a risk factor for the acceleration of age-dependent renal amyloidosis and functional impairment in mice, and suggest that obesity-enhanced chronic secretion of SAA may be the driving factor behind this process.

A nutritional nonalcoholic steatohepatitis minipig model

BACKGROUND AND AIMS

The objective of this study was to elucidate whether a Western diet was associated with nonalcoholic steatohepatitis (NASH), and the relationship between NASH, autophagy and endoplasmic reticulum (ER) stress.

METHODS

Four-month-old Lee-Sung minipigs were randomly assigned to two groups: control diet (C) and Western diet (W), for a 5-month experimental period.

RESULTS

Feeding a Western diet produced a body composition with more fat, less lean and a greater liver weight. Compared with C pigs, W pigs also exhibited an elevated level of plasma insulin and free fatty acid. The W pigs displayed glucose intolerance, lower circulation antioxidant capacity and greater hepatic oxidative stress. Furthermore, pig fed the W diets had increased collagen accumulation in the liver and elevated systemic inflammation [tumor necrosis factor α and interleukin (IL)-6]. Compared with C pigs, W pigs had higher hepatic ER stress-related protein expression of GRP94, CHOP and caspase-12. The W pigs also had greater hepatic autophagy-related protein expression of p62 and LC3II. In an obesity antibody array analysis, W pigs had higher type 2 diabetes mellitus- (insulin-like growth factor 1, osteoprotegerin and resistin), atherosclerosis- (vascular endothelial growth factor, platelet-derived growth factor-AA and plasminogen activator inhibitor-I) and inflammation- [IL-1, macrophage-stimulating protein alpha, X-linked ectodermal dysplasia receptor and serum amyloid A (SAA)] related protein expressions. In addition, W pigs had greater plasma SAA concentration than C pigs and plasma SAA level was highly associated with IL-6.

CONCLUSIONS

We successfully established a NASH pig model, and our findings suggested an association of NASH with ER stress and autophagy. The SAA has potential as a novel plasma biomarker for nonalcoholic fatty liver disease pigs.

Novel Therapies for Diabetic Kidney Disease: Storied Past and Forward Paths

IN BRIEF Current therapeutic approaches are only moderately efficacious at preventing the progression of diabetic kidney disease (DKD). As the number of people with DKD continues to rise worldwide, there is an urgent need for novel therapies. A better understanding of the root causes and molecular mechanisms of DKD pathogenesis has enabled the identification of numerous new therapeutic targets, including advanced glycation end products, reactive oxygen species, protein kinase C, and serum amyloid A. Although experimental studies have illustrated the potential of such approaches, challenges in clinical translation remain a barrier in therapeutic development. Advances in preclinical safety and efficacy evaluations and improved delivery systems may aid in clinical translation of novel DKD therapies.

Identification of a Serum amyloid A gene and the association of SNPs with Vibrio-resistance and growth traits in the clam Meretrix meretrix

Serum amyloid A (SAA), an acute response protein as well as an apolipoprotein, is considered to play crucial roles in both innate immunity and lipid metabolism. In this study, a SAA gene (MmSAA) was identified in the clam Meretrix meretrix. The full length DNA of MmSAA was 1407bp, consisting of three exons and two introns. The distribution of MmSAA in clam tissues was examined with the highest expression in hepatopancreas. In response to the Vibrio parahaemolyticus challenge, MmSAA mRNA showed significantly higher expression at 24 h post-challenge in experimental clams (P < 0.05). Forty-eight single nucleotide polymorphisms (SNPs) in the DNA partial sequence of MmSAA were discovered and examined for their association with Vibrio-resistance and growth traits, respectively. The single SNP association analysis indicated that five single SNPs (g.42, g.72, g.82, g.147 and g.165) were significantly associated with Vibrio-resistance (P < 0.05). Haplotype analysis produced additional support for association with the Chi-square values 6.393 (P = 0.012). Among the five selected SNPs, the effect of a missense mutation (g.82, A → G) was detected by site-directed mutagenesis with fusion expression of protein assay, and the result showed that the recombinant plasmids containing wild-type pET30a-MmSAA had more inhibition effect than the mutant ones on the growth rate of the host bacteria. In addition, four growth traits of the clams in 09G3SPSB population were recorded and the SNP g.176 was found to be significantly associated with the growth traits with the Global score value 0.790 (P = 0.015). Our findings suggested that common genetic variation in MmSAA might contribute to the risk of susceptibility to Vibrio infection and might be associated with the growth traits in the clams M. meretrix, and more works are still needed to validate these SNPs as potential markers for actual selective breeding.

The nitroxide radical TEMPOL prevents obesity, hyperlipidaemia, elevation of inflammatory cytokines, and modulates atherosclerotic plaque composition in apoE-/- mice

OBJECTIVE

The nitroxide compound TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl radical) has been shown to prevent obesity-induced changes in adipokines in cell and animal systems. In this study we investigated whether supplementation with TEMPOL inhibits inflammation and atherosclerosis in apoE-/- mice fed a high fat diet (HFD).

METHODS

ApoE-/- mice were fed for 12 weeks on standard chow diet or a high-fat diet. Half the mice were supplemented with 10 mg/g TEMPOL in their food. Plasma samples were analysed for triglycerides, cholesterol, low- and high-density lipoprotein cholesterol, inflammatory cytokines and markers (interleukin-6, IL-6; monocyte-chemotactic protein, MCP-1; myeloperoxidase, MPO; serum amyloid A, SAA; adiponectin; leptin). Plaques in the aortic sinus were analysed for area, and content of collagen, lipid, macrophages and smooth muscle cells.

RESULTS

High fat feeding resulted in marked increases in body mass and plasma lipid levels. Dietary TEMPOL decreased both parameters. In the high-fat-fed mice significant elevations in plasma lipid levels and the inflammatory markers IL-6, MCP-1, MPO, SAA were detected, along with an increase in leptin and a decrease in adiponectin. TEMPOL supplementation reversed these effects. When compared to HFD-fed mice, TEMPOL supplementation increased plaque collagen content, decreased lipid content and increased macrophage numbers.

CONCLUSIONS

These data indicate that in a well-established model of obesity-associated hyperlipidaemia and atherosclerosis, TEMPOL had a significant impact on body mass, atherosclerosis, hyperlipidaemia and inflammation. TEMPOL may therefore be of value in suppressing obesity, metabolic disorders and increasing atherosclerotic plaque stability.

Deletion of serum amyloid A3 improves high fat high sucrose diet-induced adipose tissue inflammation and hyperlipidemia in female mice

Serum amyloid A (SAA) increases in response to acute inflammatory stimuli and is modestly and chronically elevated in obesity. SAA3, an inducible form of SAA, is highly expressed in adipose tissue in obese mice where it promotes monocyte chemotaxis, providing a mechanism for the macrophage accumulation that occurs with adipose tissue expansion in obesity. Humans do not express functional SAA3 protein, but instead express SAA1 and SAA2 in hepatic as well as extrahepatic tissues, making it difficult to distinguish between liver and adipose tissue-specific SAA effects. SAA3 does not circulate in plasma, but may exert local effects that impact systemic inflammation. We tested the hypothesis that SAA3 contributes to chronic systemic inflammation and adipose tissue macrophage accumulation in obesity using mice deficient for Saa3 (Saa3(-/-)). Mice were rendered obese by feeding a pro-inflammatory high fat, high sucrose diet with added cholesterol (HFHSC). Both male and female Saa3(-/-) mice gained less weight on the HFHSC diet compared to Saa3(+/+) littermate controls, with no differences in body composition or resting metabolism. Female Saa3(-/-) mice, but not males, had reduced HFHSC diet-induced adipose tissue inflammation and macrophage content. Both male and female Saa3(-/-) mice had reduced liver Saa1 and Saa2 expression in association with reduced plasma SAA. Additionally, female Saa3(-/-) mice, but not males, showed improved plasma cholesterol, triglycerides, and lipoprotein profiles, with no changes in glucose metabolism. Taken together, these results suggest that the absence of Saa3 attenuates liver-specific SAA (i.e., SAA1/2) secretion into plasma and blunts weight gain induced by an obesogenic diet. Furthermore, adipose tissue-specific inflammation and macrophage accumulation are attenuated in female Saa3(-/-) mice, suggesting a novel sexually dimorphic role for this protein. These results also suggest that Saa3 influences liver-specific SAA1/2 expression, and that SAA3 could play a larger role in the acute phase response than previously thought.

Serum amyloid A-related inflammation is lowered by increased fruit and vegetable intake, while high-sensitive C-reactive protein, IL-6 and E-selectin remain unresponsive

The present study assessed whether increased fruit and vegetable (F&V) intake reduced the concentrations of the inflammatory marker serum amyloid A (SAA) in serum, HDL2 and HDL3 and whether the latter reduction influenced any of the functional properties of these HDL subfractions. The present study utilised samples from two previous studies: (1) the FAVRIT (Fruit and Vegetable Randomised Intervention Trial) study – hypertensive subjects (systolic blood pressure (BP) range 140–190 mmHg; diastolic BP range 90–110 mmHg) were randomised to receive a 1-, 3- or 6-portion F&V/d intervention for 8 weeks, and (2) the ADIT (Ageing and Dietary Intervention Trial) study – older subjects (65–85 years) were randomised to receive a 2- or 5-portion F&V/d intervention for 16 weeks. HDL2 and HDL3 were isolated by rapid ultracentrifugation. Measurements included the following: serum high-sensitive C-reactive protein (hsCRP) by an immunoturbidimetric assay; serum IL-6 and E-selectin and serum-, HDL2- and HDL3-SAA by ELISA procedures; serum-, HDL2- and HDL3-cholesterol ester transfer protein (CETP) activity by a fluorometric assay. Although the concentrations of hsCRP, IL-6 and E-selectin were unaffected by increasing F&V intake in both studies (P>0·05 for all comparisons), those of SAA in HDL3 decreased in the FAVRIT cohort (P= 0·049) and those in HDL2 and HDL3 decreased in the ADIT cohort (P= 0·035 and 0·032), which was accompanied by a decrease in the activity of CETP in HDL3 in the FAVRIT cohort (P= 0·010) and in HDL2 in the ADIT cohort (P= 0·030). These results indicate that SAA responds to increased F&V intake, while other inflammatory markers remain unresponsive, and this leads to changes in HDL2 and HDL3, which may influence their antiatherogenic potential. Overall, the present study provides tangible evidence of the effectiveness of increased F&V intake, which may be of use to health policy makers and the general public.

Particle-induced pulmonary acute phase response may be the causal link between particle inhalation and cardiovascular disease

Inhalation of ambient and workplace particulate air pollution is associated with increased risk of cardiovascular disease. One proposed mechanism for this association is that pulmonary inflammation induces a hepatic acute phase response, which increases risk of cardiovascular disease. Induction of the acute phase response is intimately linked to risk of cardiovascular disease as shown in both epidemiological and animal studies. Indeed, blood levels of acute phase proteins, such as C-reactive protein and serum amyloid A, are independent predictors of risk of cardiovascular disease in prospective epidemiological studies. In this review, we present and review emerging evidence that inhalation of particles (e.g., air diesel exhaust particles and nanoparticles) induces a pulmonary acute phase response, and propose that this induction constitutes the causal link between particle inhalation and risk of cardiovascular disease. Increased levels of acute phase mRNA and proteins in lung tissues, bronchoalveolar lavage fluid and plasma clearly indicate pulmonary acute phase response following pulmonary deposition of different kinds of particles including diesel exhaust particles, nanoparticles, and carbon nanotubes. The pulmonary acute phase response is dose-dependent and long lasting. Conversely, the hepatic acute phase response is reduced relative to lung or entirely absent. We also provide evidence that pulmonary inflammation, as measured by neutrophil influx, is a predictor of the acute phase response and that the total surface area of deposited particles correlates with the pulmonary acute phase response. We discuss the implications of these findings in relation to occupational exposure to nanoparticles.

How to cite this article: WIREs Nanomed Nanobiotechnol 2014, 6:517–531. doi: 10.1002/wnan.1279

Hypoxia increases serum amyloid A3 (SAA3) in differentiated 3T3-L1 adipocytes

Hypoxia has been implicated as a possible cause of adipose tissue inflammation. Furthermore, the acute phase protein serum amyloid A (SAA) has been associated with the modulation of the adipogenic process, and it is well-known that obese individuals have increased levels of SAA. The effect of hypoxia in the expression and production of SAA was examined in murine 3T3-L1 adipocytes. Hypoxia leads to a substantial increase in SAA3 mRNA and protein level, apparently in a time-dependent manner (threefold in 48 h), in fully differentiated 3T3-L1, followed by reestablishment of gene expression to basal levels after 24 h of reoxygenation. Hypoxia-induced SAA may be one of the key molecules to the development of the inflammatory response in adipose tissue.

Adipose tissue-derived human serum amyloid a does not affect atherosclerotic lesion area in hSAA1+/-/ApoE-/- mice

Chronically elevated serum levels of serum amyloid A (SAA) are linked to increased risk of cardiovascular disease. However, whether SAA is directly involved in atherosclerosis development is still not known. The aim of this study was to investigate the effects of adipose tissue-derived human SAA on atherosclerosis in mice. hSAA1+/- transgenic mice (hSAA1 mice) with a specific expression of human SAA1 in adipose tissue were bred with ApoE-deficient mice. The hSAA1 mice and their wild type (wt) littermates were fed normal chow for 35 weeks. At the end of the experiment, the mice were euthanized and blood, gonadal adipose tissue and aortas were collected. Plasma levels of SAA, cholesterol and triglycerides were measured. Atherosclerotic lesion areas were analyzed in the aortic arch, the thoracic aorta and the abdominal aorta in en face preparations of aorta stained with Sudan IV. The human SAA protein was present in plasma from hSAA1 mice but undetectable in wt mice. Similar plasma levels of cholesterol and triglycerides were observed in hSAA1 mice and their wt controls. There were no differences in atherosclerotic lesion areas in any sections of the aorta in hSAA1 mice compared to wt mice. In conclusion, our data suggest that adipose tissue-derived human SAA does not influence atherosclerosis development in mice.

Obesity and its metabolic complications: the role of adipokines and the relationship between obesity, inflammation, insulin resistance, dyslipidemia and nonalcoholic fatty liver disease

Accumulating evidence indicates that obesity is closely associated with an increased risk of metabolic diseases such as insulin resistance, type 2 diabetes, dyslipidemia and nonalcoholic fatty liver disease. Obesity results from an imbalance between food intake and energy expenditure, which leads to an excessive accumulation of adipose tissue. Adipose tissue is now recognized not only as a main site of storage of excess energy derived from food intake but also as an endocrine organ. The expansion of adipose tissue produces a number of bioactive substances, known as adipocytokines or adipokines, which trigger chronic low-grade inflammation and interact with a range of processes in many different organs. Although the precise mechanisms are still unclear, dysregulated production or secretion of these adipokines caused by excess adipose tissue and adipose tissue dysfunction can contribute to the development of obesity-related metabolic diseases. In this review, we focus on the role of several adipokines associated with obesity and the potential impact on obesity-related metabolic diseases. Multiple lines evidence provides valuable insights into the roles of adipokines in the development of obesity and its metabolic complications. Further research is still required to fully understand the mechanisms underlying the metabolic actions of a few newly identified adipokines.