Acute-phase serum amyloid A protein and its implication in the development of type 2 diabetes in the KORA S4/F4 study

Establishment and validation of a nomogram to predict postoperative anemia after total hip arthroplasty

BACKGROUND

Anemia is a common complication of total hip arthroplasty (THA). In this study, we evaluated the preoperative risk factors for postoperative anemia after THA and developed a nomogram model based on related preoperative and intraoperative factors.

METHODS

From January 2020 to May 2023, 927 THA patients at the same medical center were randomly assigned to either the training or validation cohort. The correlation between preoperative and intraoperative risk factors and postoperative anemia after THA was evaluated using univariate and multivariate logistic regression analysis. A nomogram was developed using these predictive variables. The effectiveness and validation for the clinical application of this nomogram were evaluated using the concordance index (C-index), receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA).

RESULTS

Through univariate and multivariate logistic regression analysis, 7 independent predictive factors were identified in the training cohort: Lower body mass index (BMI), extended operation time, greater intraoperative bleeding, lower preoperative hemoglobin level, abnormally high preoperative serum amyloid A (SAA) level, history of cerebrovascular disease, and history of osteoporosis. The C-index of the model was 0.871, while the AUC indices for the training and validation cohorts were 84.4% and 87.1%, respectively. In addition, the calibration curves of both cohorts showed excellent consistency between the observed and predicted probabilities. The DCA curves of the training and validation cohorts were high, indicating the high clinical applicability of the model.

CONCLUSIONS

Lower BMI, extended operation time, increased intraoperative bleeding, reduced preoperative hemoglobin level, elevated preoperative SAA level, history of cerebrovascular disease, and history of osteoporosis were seven independent preoperative risk factors associated with postoperative anemia after THA. The nomogram developed could aid in predicting postoperative anemia, facilitating advanced preparation, and enhancing blood management. Furthermore, the nomogram could assist clinicians in identifying patients most at risk for postoperative anemia.

Plasma Proteomic Signature of Endometrial Cancer in Patients with Diabetes

The incidence and mortality of endometrial cancer (EC) have increased in recent years. There is mounting evidence that diabetes may play a role in the greater incidence of EC. The molecular mechanisms of the interaction between type 2 diabetes and EC are not yet clearly understood yet. The present study was undertaken to investigate the plasma proteomics of EC patients with diabetes in comparison to those of EC patients without diabetes. Plasma samples were obtained from age-matched patients (EC diabetic and EC nondiabetic). Untargeted proteomic analysis was carried out using a two-dimensional differential gel electrophoresis coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Of the 33 proteins identified, which significantly differed in the plasma abundance between groups, 17 were upregulated and 16 were downregulated. The majority of the altered proteins are involved in the acute phase reaction, cholesterol metabolism, scavenging of heme from plasma, and plasma lipoprotein assembly and mobilization. α-2-macroglobulin, Ras association domain-containing protein 3, apolipoprotein A-I, α-1B-glycoprotein, and zinc-α-2-glycoprotein were significantly upregulated. The significantly downregulated proteins included haptoglobin, apolipoprotein A-IV, hemopexin, and α-1-antichymotrypsin. The differential expression of proteins found in patients who had EC and diabetes indicated severe disease and a poor prognosis. The protein interaction analysis showed dysregulation of cholesterol metabolism and heme scavenging pathways in these patients.

Current views on selenoprotein S in the pathophysiological processes of diabetes-induced atherosclerosis: potential therapeutics and underlying biomarkers

Atherosclerotic cardiovascular disease (ASCVD) consistently ranks as the primary mortality factor among diabetic people. A thorough comprehension of the pathophysiological routes and processes activated by atherosclerosis (AS) caused by diabetes mellitus (DM), together with the recognition of new contributing factors, could lead to the discovery of crucial biomarkers and the development of innovative drugs against atherosclerosis. Selenoprotein S (SELENOS) has been implicated in the pathology and progression of numerous conditions, including diabetes, dyslipidemia, obesity, and insulin resistance (IR)-all recognized contributors to endothelial dysfunction (ED), a precursor event to diabetes-induced AS. Hepatic-specific deletion of SELENOS accelerated the onset and progression of obesity, impaired glucose tolerance and insulin sensitivity, and increased hepatic triglycerides (TG) and diacylglycerol (DAG) accumulation; SELENOS expression in subcutaneous and omental adipose tissue was elevated in obese human subjects, and act as a positive regulator for adipogenesis in 3T3-L1 preadipocytes; knockdown of SELENOS in Min6 β-cells induced β-cell apoptosis and reduced cell proliferation. SELENOS also participates in the early stages of AS, notably by enhancing endothelial function, curbing the expression of adhesion molecules, and lessening leukocyte recruitment-actions that collectively reduce the formation of foam cells. Furthermore, SELENOS forestalls the apoptosis of vascular smooth muscle cells (VSMCs) and macrophages, mitigates vascular calcification, and alleviates inflammation in macrophages and CD4+ T cells. These actions help stifle the creation of unstable plaque characterized by thinner fibrous caps, larger necrotic cores, heightened inflammation, and more extensive vascular calcification-features seen in advanced atherosclerotic lesion development. Additionally, serum SELENOS could function as a potential biomarker, and SELENOS single nucleotide polymorphisms (SNPs) rs4965814, rs28628459, and rs9806366, might be effective gene markers for atherosclerosis-related diseases in diabetes. This review accentuates the pathophysiological processes of atherosclerosis in diabetes and amasses current evidence on SELENOS's potential therapeutic benefits or as predictive biomarkers in the various stages of diabetes-induced atherosclerosis.

Inflammatory proteins are associated with mortality in a middle-aged diverse cohort

BACKGROUND

Recent data indicate a decline in overall longevity in the United States. Even prior to the COVID-19 pandemic, an increase in midlife mortality rates had been reported. Life expectancy disparities have persisted in the United States for racial and ethnic groups and for individuals living at low socioeconomic status. These continued trends in mortality indicate the importance of examining biomarkers of mortality at midlife in at-risk populations. Circulating levels of cytokines and inflammatory markers reflect systemic chronic inflammation, which is a well-known driver of many age-related diseases.

METHODS

In this study, we examined the relationship of nine different inflammatory proteins with mortality in a middle-aged socioeconomically diverse cohort of African-American and White men and women (n = 1122; mean age = 47.8 years).

RESULTS

We found significant differences in inflammatory-related protein serum levels between African-American and White middle-aged adults. E-selectin and fibrinogen were significantly higher in African-American adults. IFN-γ, TNF-α trimer, monocyte chemoattractant protein-1 (MCP-1), soluble receptor for advanced glycation end-products (sRAGE) and P-selectin were significantly higher in White participants compared to African-American participants. Higher levels of E-selectin, MCP-1 and P-selectin were associated with a higher mortality risk. Furthermore, there was a significant interaction between sex and IL-6 with mortality. IL-6 levels were associated with an increased risk of mortality, an association that was significantly greater in women than men. In addition, White participants with high levels of sRAGE had significantly higher survival probability than White participants with low levels of sRAGE, while African-American participants had similar survival probabilities across sRAGE levels.

CONCLUSIONS

These results suggest that circulating inflammatory markers can be utilized as indicators of midlife mortality risk in a socioeconomically diverse cohort of African-American and White individuals.

The impact of forced displacement: trauma, increased levels of inflammation and early presentation of diabetes in women Syrian refugees

BACKGROUND

Forced displacement and war trauma cause high rates of post-traumatic stress, anxiety disorders and depression in refugee populations. We investigated the impact of forced displacement on mental health status, gender, presentation of type 2 diabetes (T2D) and associated inflammatory markers among Syrian refugees in Lebanon.

METHODS

Mental health status was assessed using the Harvard Trauma Questionnaire (HTQ) and the Hopkins Symptom Checklist-25 (HSCL-25). Additional metabolic and inflammatory markers were analyzed.

RESULTS

Although symptomatic stress scores were observed in both men and women, women consistently displayed higher symptomatic anxiety/depression scores with the HSCL-25 (2.13 ± 0.58 versus 1.95 ± 0.63). With the HTQ, however, only women aged 35-55 years displayed symptomatic post-traumatic stress disorder (PTSD) scores (2.18 ± 0.43). Furthermore, a significantly higher prevalence of obesity, prediabetes and undiagnosed T2D were observed in women participants (23.43, 14.91 and 15.18%, respectively). Significantly high levels of the inflammatory marker serum amyloid A were observed in women (11.90 ± 11.27 versus 9.28 ± 6.93, P = 0.036).

CONCLUSIONS

Symptomatic PTSD, anxiety/depression coupled with higher levels of inflammatory marker and T2D were found in refugee women aged between 35 and 55 years favoring the strong need for psychosocial therapeutic interventions in moderating stress-related immune dysfunction and development of diabetes in this subset of female Syrian refugees.

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.

Evaluation of Pentraxin 3 and Serum Amyloid A in the Gingival Crevicular Fluid of Patients with Periodontal Disease and Obesity

BACKGROUND

Pentraxin 3 (PTX3) is associated with periodontal tissue inflammation, a condition that precedes alveolar bone resorption. It is also elevated in obese tissues and is a useful biomarker of proinflammatory status. Serum amyloid A (SAA) is a proinflammatory and lipolytic adipokine. Adipocytes strongly express SAA, which suggests that it may have a significant role in the production of free fatty acids and local and systemic inflammation.

MATERIALS AND METHODS

We statistically analyzed the gingival crevicular fluid (GCF) values of PTX3 and SAA in patients with periodontal disease, who were diagnosed with obesity, and compared them with the values of inflammatory markers from patients diagnosed with one of the diseases and with healthy patients.

RESULTS

The patients with obesity and periodontitis had significantly higher levels of PTX3 and SAA than the patients diagnosed with either obesity or periodontitis.

CONCLUSIONS

These two markers are involved in the association between the two pathologies, as evidenced by the correlations between these levels and some clinical parameters.

NOD-like Receptors-Emerging Links to Obesity and Associated Morbidities

Obesity and its associated metabolic morbidities have been and still are on the rise, posing a major challenge to health care systems worldwide. It has become evident over the last decades that a low-grade inflammatory response, primarily proceeding from the adipose tissue (AT), essentially contributes to adiposity-associated comorbidities, most prominently insulin resistance (IR), atherosclerosis and liver diseases. In mouse models, the release of pro-inflammatory cytokines such as TNF-alpha (TNF-α) and interleukin (IL)-1β and the imprinting of immune cells to a pro-inflammatory phenotype in AT play an important role. However, the underlying genetic and molecular determinants are not yet understood in detail. Recent evidence demonstrates that nucleotide-binding and oligomerization domain (NOD)-like receptor (NLR) family proteins, a group of cytosolic pattern recognition receptors (PRR), contribute to the development and control of obesity and obesity-associated inflammatory responses. In this article, we review the current state of research on the role of NLR proteins in obesity and discuss the possible mechanisms leading to and the outcomes of NLR activation in the obesity-associated morbidities IR, type 2 diabetes mellitus (T2DM), atherosclerosis and non-alcoholic fatty liver disease (NAFLD) and discuss emerging ideas about possibilities for NLR-based therapeutic interventions of metabolic diseases.

Emerging roles of selenium on metabolism and type 2 diabetes

Selenium is recognized as an essential element for human health and enters human body mainly via diet. Selenium is a key constituent in selenoproteins, which exert essential biological functions, including antioxidant and anti-inflammatory effects. Several selenoproteins including glutathione peroxidases, selenoprotein P and selenoprotein S are known to play roles in the regulation of type 2 diabetes. Although there is a close association between certain selenoproteins with glucose metabolism or insulin resistance, the relationship between selenium and type 2 diabetes is complex and remains uncertain. Here we review recent advances in the field with an emphasis on roles of selenium on metabolism and type 2 diabetes. Understanding the association between selenium and type 2 diabetes is important for developing clinical practice guidelines, establishing and implementing effective public health policies, and ultimately combating relative health issues.

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.

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.

Serum Amyloid A1 Exacerbates Hepatic Steatosis via TLR4 Mediated NF-κB Signaling Pathway

Objective

Chronic inflammatory response plays a prominent role in obesity-related nonalcoholic fatty liver disease (NAFLD). However, the intrahepatic triggering mechanism of inflammation remains obscure. This study aimed to elucidate the role of serum amyloid A1 (SAA1), an acute-phase response protein, in the obesity-induced hepatic inflammation and NAFLD.

Methods

Male mice were fed a high fat diet (HFD) for 16 weeks, and insulin resistance, hepatic steatosis, and inflammation in mice were monitored. Murine SAA1/2 was genetically manipulated to investigate the role of SAA1 in NAFLD.

Results

We found that SAA1 was increased in the NAFLD liver in both humans and mice. Knockout of SAA1/2 or knockdown of hepatic SAA1/2 promoted energy expenditure and alleviated HFD-induced metabolic disorder, hepatic steatosis, and inflammation. Endogenous overexpression of SAA1 in hepatocytes by adeno-associated virus 8 (AAV8) transfection aggravated overnutrition-associated gain of body weight, insulin resistance, hepatic lipid accumulation, and liver injury, which were markedly alleviated by knockout of murine toll-like receptor 4 (TLR4). Mechanistically, SAA1 directly bound with TLR4/myeloid differentiation 2 (MD2) to induce TLR4 internalization, leading to the activation of nuclear factor (NF)-κB signaling and production of both SAA1 and other inflammatory cytokines, including interleukin (IL)-6 and C–C chemokine ligand (CCL2) in hepatocytes. Administration of HFD mice with an AAV8-shRNA-SAA1/2 showed a therapeutic effect on hepatic inflammation and NAFLD progression.

Conclusions

These results demonstrate that SAA1 triggers hepatic steatosis and intrahepatic inflammatory response by forming a SAA1/TLR4/NF-κB/SAA1 feedforward regulatory circuit, which, in turn, leads to NAFLD progression. SAA1 may act as a potential target for the disease intervention.

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SAA1/2 deficiency alleviates HFD-induced hepatic steatosis and inflammation in mice.

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SAA1 aggravating overnutrition-associated hepatic steatosis and inflammation is dependent on TLR4.

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SAA1 directly binds to TLR4/MD2 to induce TLR4 internalization, leading to the activation of NF-κB signaling .

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SAA1/TLR4/NF-κB/SAA1 positive feedback in hepatocytes may be a potential target for obesity associated NAFLD.

Associations of serum amyloid A and 25-hydroxyvitamin D with diabetic nephropathy: A cross-sectional study

BACKGROUND

The present study investigated the relationships between serum amyloid A (SAA), 25-hydroxyvitamin D (25(OH)VD) and diabetic nephropathy (DN) to provide evidence for the prevention and management of DN.

METHODS

A total of 182 patients with type 2 diabetes mellitus (T2DM) were enrolled in this study. The levels of SAA, 25(OH)VD, and other conventional indicators were measured and analyzed. Receiver operating characteristic curve analysis was applied for the combined measurement of SAA and 25(OH)VD, and risk factors for DN were evaluated using binary logistic regression analysis.

RESULTS

The levels of SAA in T2DM patients were significantly higher than those in healthy subjects, and the level significantly increased with the progression of DN (p < 0.05). In contrast, the level of 25(OH)VD in T2DM patients was significantly lower than that in healthy subjects, and the level significantly decreased with the progression of DN (p < 0.05). The combined measurement of SAA and 25(OH)VD distinguished DN patients from T2DM patients better than the measurement of SAA or 25(OH)VD alone. SAA was an independent risk factor for DN, and 25(OH)VD was an independent protective factor for DN.

CONCLUSION

SAA and 25(OH)VD might be used as potential markers to identify patients at increased risk of developing DN.

Elevated SAA1 promotes the development of insulin resistance in ovarian granulosa cells in polycystic ovary syndrome

BACKGROUND

Insulin resistance (IR) contributes to ovarian dysfunctions in polycystic ovarian syndrome (PCOS) patients. Serum amyloid A1 (SAA1) is an acute phase protein produced primarily by the liver in response to inflammation. In addition to its role in inflammation, SAA1 may participate in IR development in peripheral tissues. Yet, expressional regulation of SAA1 in the ovary and its role in the pathogenesis of ovarian IR in PCOS remain elusive.

METHODS

Follicular fluid, granulosa cells and peripheral venous blood were collected from PCOS and non-PCOS patients with and without IR to measure SAA1 abundance for analysis of its correlation with IR status. The effects of SAA1 on its own expression and insulin signaling pathway were investigated in cultured primary granulosa cells.

RESULTS

Ovarian granulosa cells were capable of producing SAA1, which could be induced by SAA1 per se. Moreover, the abundance of SAA1 significantly increased in granulosa cells and follicular fluid in PCOS patients with IR. SAA1 treatment significantly attenuated insulin-stimulated membrane translocation of glucose transporter 4 and glucose uptake in granulosa cells through induction of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression with subsequent inhibition of Akt phosphorylation. These effects of SAA1 could be blocked by inhibitors for toll-like receptors 2/4 (TLR 2/4) and nuclear factor kappa light chain enhancer of activated B (NF-κB).

CONCLUSIONS

Human granulosa cells are capable of feedforward production of SAA1, which significantly increased in PCOS patients with IR. Excessive SAA1 reduces insulin sensitivity in granulosa cells via induction of PTEN and subsequent inhibition of Akt phosphorylation upon activation of TLR2/4 and NF-κB pathway. These findings highlight that elevation of SAA1 in the ovary promotes the development of IR in granulosa cells of PCOS patients.

Shared metabolic and neuroimmune mechanisms underlying Type 2 Diabetes Mellitus and Major Depressive Disorder

Type 2 Diabetes Mellitus (T2DM) is a chronic metabolic disease with symptoms that go beyond the domain of glucose metabolism. In fact, research has shown that T2DM is accompanied by neurodegeneration and neuroinflammation. Interestingly, Major Depressive Disorder (MDD), a mood disorder characterized mainly by depressed mood and anhedonia is a key feature of T2DM. A body of evidence demonstrates that there are many shared neuroimmune mechanisms underlying the pathophysiology of T2DM and MDD. Therefore, here we review the state-of-art regarding the underlying factors common to both T2DM and MDD. Furthermore, we briefly discuss how depressive symptoms in diabetic patients could be tackled by using novel therapeutic approaches uncovered by these shared mechanisms. Understanding the comorbidity of depression in diabetic patients is essential to fully address T2DM pathophysiology and treatment.

Pro-Inflammatory Serum Amyloid a Stimulates Renal Dysfunction and Enhances Atherosclerosis in Apo E-Deficient Mice

Acute serum amyloid A (SAA) is an apolipoprotein that mediates pro-inflammatory and pro-atherogenic pathways. SAA-mediated signalling is diverse and includes canonical and acute immunoregulatory pathways in a range of cell types and organs. This study aimed to further elucidate the roles for SAA in the pathogenesis of vascular and renal dysfunction. Two groups of male ApoE-deficient mice were administered SAA (100 µL, 120 µg/mL) or vehicle control (100 µL PBS) and monitored for 4 or 16 weeks after SAA treatment; tissue was harvested for biochemical and histological analyses at each time point. Under these conditions, SAA administration induced crosstalk between NF-κB and Nrf2 transcriptional factors, leading to downstream induction of pro-inflammatory mediators and antioxidant response elements 4 weeks after SAA administration, respectively. SAA treatment stimulated an upregulation of renal IFN-γ with a concomitant increase in renal levels of p38 MAPK and matrix metalloproteinase (MMP) activities, which is linked to tissue fibrosis. In the kidney of SAA-treated mice, the immunolocalisation of inducible nitric oxide synthase (iNOS) was markedly increased, and this was localised to the parietal epithelial cells lining Bowman’s space within glomeruli, which led to progressive renal fibrosis. Assessment of aortic root lesion at the study endpoint revealed accelerated atherosclerosis formation; animals treated with SAA also showed evidence of a thinned fibrous cap as judged by diffuse collagen staining. Together, this suggests that SAA elicits early renal dysfunction through promoting the IFN-γ-iNOS-p38 MAPK axis that manifests as the fibrosis of renal tissue and enhanced cardiovascular disease.

Serum Amyloid A Promotes Inflammation-Associated Damage and Tumorigenesis in a Mouse Model of Colitis-Associated Cancer

BACKGROUND & AIMS

Identifying new approaches to lessen inflammation, as well as the associated malignant consequences, remains crucial to improving the lives and prognosis of patients diagnosed with inflammatory bowel diseases. Although it previously has been suggested as a suitable biomarker for monitoring disease activity in patients diagnosed with Crohn's disease, the role of the acute-phase protein serum amyloid A (SAA) in inflammatory bowel disease remains unclear. In this study, we aimed to assess the role of SAA in colitis-associated cancer.

METHODS

We established a model of colitis-associated cancer in wild-type and SAA double-knockout (Saa1/2-/-) mice by following the azoxymethane/dextran sulfate sodium protocol. Disease activity was monitored throughout the study while colon and tumor tissues were harvested for subsequent use in cytokine analyses, Western blot, and immunohistochemistry +experiments.

RESULTS

We observed attenuated disease activity in mice deficient for Saa1/2 as evidenced by decreased weight loss, increased stool consistency, decreased rectal bleeding, and decreased colitis-associated tissue damage. Macrophage infiltration, including CD206+ M2-like macrophages, also was attenuated in SAA knockout mice, while levels of interleukin 4, interleukin 10, and tumor necrosis factor-ɑ were decreased in the distal colon. Mice deficient for SAA also showed a decreased tumor burden, and tumors were found to have increased apoptotic activity coupled with decreased expression for markers of proliferation.

CONCLUSION

Based on these findings, we conclude that SAA has an active role in inflammatory bowel disease and that it could serve as a therapeutic target aimed at decreasing chronic inflammation and the associated risk of developing colitis-associated cancer.

Mechanisms of NLRP3 priming in inflammaging and age related diseases

The NLRP3 inflammasome is a vital part of the innate immune response, whilst its aberrant activation drives the progression of a number of non-communicable diseases. Thus, NLRP3 inflammasome assembly must be tightly controlled at several checkpoints. The priming step of NLRP3 inflammasome activation is associated with increased NLRP3 gene expression, as well as post-translational modifications that control NLRP3 levels and licence the NLRP3 protein for inflammasome assembly. Increasing life expectancy in modern society is accompanied by a growing percentage of elderly individuals. The process of aging is associated with chronic inflammation that drives and/or worsens a range of age related non-communicable conditions. The NLRP3 inflammasome is known to contribute to pathological inflammation in many settings, but the mechanisms that prime NLRP3 for activation throughout aging and related co-morbidities have not been extensively reviewed. Here we dissect the biochemical changes that occur during aging and the pathogenesis of age related diseases and analyse the mechanisms by which they prime the NLRP3 inflammasome, thus exacerbating inflammation.

Associations of Innate and Adaptive Immune Cell Subsets With Incident Type 2 Diabetes Risk: The MESA Study

OBJECTIVE

Cell-mediated immunity is implicated in glucose homeostasis and insulin resistance. Whether the levels of innate and adaptive immune cells in peripheral blood are risk factors for incident type 2 diabetes (T2D) remains unknown. We hypothesized that the proportions of naive, memory, CD28-, Th17, and T regulatory CD4+ cells would be associated with incident T2D. In secondary analyses, we evaluated the relationships of 28 additional immune cell phenotypes with T2D.

DESIGN

Immune cell phenotypes (n = 33) were measured by flow cytometry using cryopreserved cells collected from 1113 participants of the Multi-Ethnic Study of Atherosclerosis (MESA) at the baseline examination (2000-2002). Cox proportional hazards models were used to evaluate associations of immune cell phenotypes with incident T2D over a median follow-up of 9.1 years, adjusted for age, sex, race/ethnicity, educational status, and body mass index.

RESULTS

Incident T2D was observed for 120 participants. None of the cell phenotypes included in the primary hypotheses were significantly associated with T2D (all P > 0.05). Among the secondary immune cells studied, a higher proportion of CD19+CD27+ B cells was associated with a reduced risk of T2D (hazard ratio: 0.72 (95% confidence interval: 0.56, 0.93), per 1-standard deviation (16%) increase). This association was no longer significant after correction for the multiple cell phenotypes tested (P > 0.0015).

CONCLUSIONS

Our results suggest that the frequencies of several subsets of monocytes, innate lymphocytes, and CD4+ and CD8+ T cells in circulating blood are not related to the future onset of T2D. Higher levels of CD19+CD27+ B cells may be associated with decreased T2D risk.

Serum amyloid A is not incorporated into HDL during HDL biogenesis

Liver-derived serum amyloid A (SAA) is present in plasma where it is mainly associated with HDL and from which it is cleared more rapidly than are the other major HDL-associated apolipoproteins. Although evidence suggests that lipid-free and HDL-associated forms of SAA have different activities, the pathways by which SAA associates and disassociates with HDL are poorly understood. In this study, we investigated SAA lipidation by hepatocytes and how this lipidation relates to the formation of nascent HDL particles. We also examined hepatocyte-mediated clearance of lipid-free and HDL-associated SAA. We prepared hepatocytes from mice injected with lipopolysaccharide or an SAA-expressing adenoviral vector. Alternatively, we incubated primary hepatocytes from SAA-deficient mice with purified SAA. We analyzed conditioned media to determine the lipidation status of endogenously produced and exogenously added SAA. Examining the migration of lipidated species, we found that SAA is lipidated and forms nascent particles that are distinct from apoA-I-containing particles and that apoA-I lipidation is unaltered when SAA is overexpressed or added to the cells, indicating that SAA is not incorporated into apoA-I-containing HDL during HDL biogenesis. Like apoA-I formation, generation of SAA-containing particles was dependent on ABCA1, but not on scavenger receptor class B type I. Hepatocytes degraded significantly more SAA than apoA-I. Taken together, our results indicate that SAA's lipidation and metabolism by the liver is independent of apoA-I and that SAA is not incorporated into HDL during HDL biogenesis.

Adrenoceptor-stimulated inflammatory response in stress-induced serum amyloid A synthesis

RATIONALE

Stressful life events are suggested to contribute to the development of various pathologies, such as cardiovascular disorders, whose etiopathogenesis is highly associated with elevated levels of serum amyloid A (SAA) proteins. SAA synthesis in the liver is regulated by a complex network of cytokines acting independently or in concert with various hormones/stimulants including the stress-activated sympathetic nervous system.

OBJECTIVE

This study aims to investigate the underlying mechanisms that regulate the stress-induced hepatic synthesis of SAA, with particular focus on adrenoceptors (AR), major components of the sympathoadrenal response to stress.

METHODS AND RESULTS

We demonstrated that repeated stress elevates IL-1β, IL-6, and TNFα serum levels in mice, accompanied by increased synthesis and secretion of hepatic SAA1/2 and SAA3, an effect that was blocked by AR antagonists. Moreover, stimulation of α₁- and β_1/2-ARs mimics the stress effect on SAA1/2 regulation, whereas α₂-AR stimulation exhibits a relatively weak impact on SAA. In support of the essential cytokine contribution in the AR-agonist induced SAA production is the fact that the anti-inflammatory drug, sodium salicylate, prevented the AR-stimulated hepatic SAA1/2 synthesis by reducing IL-1β levels, whereas IL-1β inhibition with Anakinra mimics this sodium salicylate preventive effect, thus indicating a crucial role for IL-1β. Interestingly, the AR-driven SAA3 synthesis was elevated by sodium salicylate in a TNFα-dependent way, supporting diverse and complex regulatory roles of cytokines in SAA production. In contrast to α₁/α₂-AR, the β_1/2-AR-mediated SAA1/2 and SAA3 upregulation cannot be reversed by fenofibrate, a hypolipidemic drug with anti-inflammatory properties.

CONCLUSION

Taken together, these findings strongly support a critical role of the AR-stimulated inflammatory response in the hepatic SAA production under stressful conditions, highlighting distinct AR type-specific mechanisms that regulate the hepatic synthesis of SAA1/2 and SAA3.

The prognostic value of serum amyloid A for long-term mortality among patients with subclinical carotid atherosclerosis

BACKGROUND AND PURPOSE

Despite extensive research in the last decade, the role of serum amyloid A (SAA) in atherogenesis remains highly controversial. The aim of this study was therefore to assess whether SAA is associated with long-term mortality in patients with subclinical carotid artery disease.

METHODS

One thousand sixty-five patients with neurological asymptomatic carotid atherosclerosis as evaluated by duplex sonography were prospectively followed for cause-specific mortality.

RESULTS

During a median of 11.8 years, a total of 549 deaths, including 362 cardiovascular deaths, were recorded. Patients who died within the follow-up period had significantly higher baseline SAA serum levels compared to those who survived (12.9 vs 9.5 mg/dL; P < 0.001). In univariable Cox regression analysis, the risk of all-cause and cardiovascular mortality significantly increased in patients with elevated serum levels of SAA (crude hazard ratio for cardiovascular mortality per increase of 1 SD of SAA levels was 1.14, 95% CI 1.08-1.22], P < 0.0001). However, SAA lost its significance after adjusting for high-sensitivity C-reactive protein (hsCRP), suggesting that SAA might not be directly associated with atherogenesis, but rather be a mere reflection of the individual patient's inflammatory status.

CONCLUSIONS

Serum amyloid A is not independently associated with (cardiovascular) mortality in patients with subclinical carotid atherosclerosis.

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.

Serum Amyloid A Contributes to Chronic Apical Periodontitis via TLR2 and TLR4

In the current concept of bacterial infections, pathogen-associated molecular patterns (PAMPs) derived from pathogens and damage-associated molecular patterns (DAMPs) released from damaged/necrotic host cells are crucial factors in induction of innate immune responses. However, the implication of DAMPs in apical and marginal periodontitis is unknown. Serum amyloid A (SAA) is a DAMP that is involved in the development of various chronic inflammatory diseases, such as rheumatoid arthritis. In the present study, we tested whether SAA is involved in the pathogenesis of periapical lesions, using human periapical surgical specimens and mice deficient in SAA and Toll-like receptors (TLR). SAA1/2 was locally expressed in human periapical lesions at the mRNA and protein levels. The level of SAA protein appeared to be positively associated with the inflammatory status of the lesions. In the development of mouse periapical inflammation, SAA1.1/2.1 was elevated locally and systemically in wild-type (WT) mice. Although SAA1.1/2.1 double-knockout and SAA3 knockout mice had redundant attenuation of the extent of periapical lesions, these animals showed strikingly improved inflammatory cell infiltration versus WT. Recombinant human SAA1 (rhSAA1) directly induced chemotaxis of WT neutrophils in a dose-dependent manner in vitro. In addition, rhSAA1 stimulation significantly prolonged the survival of WT neutrophils as compared with nonstimulated neutrophils. Furthermore, rhSAA1 activated the NF-κB pathway and subsequent IL-1α production in macrophages in a dose-dependent manner. However, TLR2/TLR4 double deficiency substantially diminished these SAA-mediated proinflammatory responses. Taken together, the SAA-TLR axis plays an important role in the chronicity of periapical inflammation via induction of inflammatory cell infiltration and prolonged cell survival. The interactions of PAMPs and DAMPs require further investigation in dental/oral inflammation.

Effects of β-glucan and Vitamin D Supplementation on Inflammatory Parameters in Patients with Diabetic Retinopathy

The objective of this article is to evaluate the potential effects of beta-glucan and vitamin D supplementation in patients with diabetic retinopathy. We evaluated the levels of several parameters of inflammatory reactions (C-reactive protein [CRP], serum amyloid A [SAA], and interleukin- [IL-] 6), leptin, and vitamin D. Using a 3-month interval, we divided the patients into three groups: (1) supplemented with beta-glucan and vitamin D, (2) supplemented with vitamin D and placebo, and (3) supplemented with vitamin D alone. By this division, we aim not only to observe whether beta-glucan can increase the effects of vitamin D, but also to eliminate the potential effects of placebo. The doses of vitamin D corresponded to phototype, weight, age, and sex of the individual. Fifty-two diabetic retinopathy patients were selected for our study. We found significant vitamin D deficits in all cases, even after three months of supplementation with vitamin D. Significant changes in levels of CRP were observed in the beta-glucan-supplemented group; levels of SAA and IL-6 were not changed. Leptin levels were significantly lowered in the beta-glucan-supplemented group and increased in the other groups. More detailed studies and/or longer supplementation is necessary.

Higher n-6:n-3 Fatty Acid Intake Is Associated with Decreased Cardiometabolic Risk Factors in a Racially Diverse Sample of Children

BACKGROUND

Accumulating evidence implicates diet quality in childhood as playing a significant role in adult cardiometabolic health. Polyunsaturated fatty acids (PUFAs) of the n-6 (ω-6) and n-3 (ω-3) series contribute unique protective effects against cardiometabolic disease. As such, the ratio between n-6 and n-3 PUFAs is a dietary metric of interest in the early life span, although an optimum intake ratio has yet to be determined.

OBJECTIVE

This cross-sectional study assesses relations between the ratio of total n-6:n-3 PUFA intake and cardiometabolic risk factors in a racially diverse sample of children (n = 191) from the Admixture Mapping of Ethnic and Racial Insulin Complex Outcomes (AMERICO) study.

METHODS

Outcome measures included waist circumference, lipid concentrations, fasting glucose, and two 24-h dietary recalls from boys and girls aged 7-12 y who self-reported as European American (n = 81), African American (n = 55), or Hispanic American (n = 55). Linear regression analyses were used to assess associations between predictors of interest and outcomes after adjusting for covariates.

RESULTS

PUFA intake reflected in the n-6:n-3 ratio was inversely associated with concentrations of total and LDL cholesterol [β ± SE: -0.359 ± 0.107 (P = 0.001) and -0.189 ± 0.069 (P = 0.007), respectively]. Exploratory analyses showed that the intake of total n-6 PUFAs was not significantly predictive of any cardiometabolic risk factor assessed, whereas total n-3 PUFA intake was positively associated with concentrations of HDL cholesterol (β ± SE: 0.114 ± 0.042; P = 0.007).

CONCLUSIONS

Results suggest that the effect of n-6 and n-3 PUFA intake reflected in the ratio may be largely driven by n-3 PUFAs in reducing 2 lipid cardiometabolic risk factors among this multiethnic cohort of children. Until an ideal intake ratio is determined, nutritional counseling should focus on meeting recommended levels of both n-3 and n-6 PUFAs in order to establish beneficial childhood dietary patterns that may positively influence adult cardiometabolic health.

Vegetated land cover near residence is associated with reduced allostatic load and improved biomarkers of neuroendocrine, metabolic and immune functions

BACKGROUND

Greater exposure to urban green spaces has been linked to reduced risks of depression, cardiovascular disease, diabetes and premature death. Alleviation of chronic stress is a hypothesized pathway to improved health. Previous studies linked chronic stress with a biomarker-based composite measure of physiological dysregulation known as allostatic load.

OBJECTIVE

This study's objective was to assess the relationship between vegetated land cover near residences and allostatic load.

METHODS

This cross-sectional population-based study involved 206 adult residents of the Durham-Chapel Hill, North Carolina metropolitan area. Exposure was quantified using high-resolution metrics of trees and herbaceous vegetation within 500m of each residence derived from the U.S. Environmental Protection Agency's EnviroAtlas land cover dataset. Eighteen biomarkers of immune, neuroendocrine, and metabolic functions were measured in serum or saliva samples. Allostatic load was defined as a sum of potentially unhealthy biomarker values dichotomized at 10th or 90th percentile of sample distribution. Regression analysis was conducted using generalized additive models with two-dimensional spline smoothing function of geographic coordinates, weighted measures of vegetated land cover allowing decay of effects with distance, and geographic and demographic covariates.

RESULTS

An inter-quartile range increase in distance-weighted vegetated land cover was associated with 37% (95% Confidence Limits 46%; 27%) reduced allostatic load; significantly reduced adjusted odds of having low level of norepinephrine, dopamine, and dehydroepiandrosterone, and high level of epinephrine, fibrinogen, vascular cell adhesion molecule-1, and interleukin-8 in serum, and α-amylase in saliva; and reduced odds of previously diagnosed depression.

CONCLUSIONS

The observed effects of vegetated land cover on allostatic load and individual biomarkers are consistent with prevention of depression, cardiovascular disease and premature mortality.

Lipopolysaccharide-binding protein (LBP) reverses the amyloid state of fibrin seen in plasma of type 2 diabetics with cardiovascular co-morbidities

Type 2 diabetes (T2D) has many cardiovascular complications, including a thrombotic propensity. Many such chronic, inflammatory diseases are accompanied (and may be exacerbated, and possibly even largely caused) by amyloid fibril formation. Recognising that there are few strong genetic associations underpinning T2D, but that amyloidogenesis of amylin is closely involved, we have been seeking to understand what might trigger the disease. Serum levels of bacterial lipopolysaccharide are raised in T2D, and we recently showed that fibrin(ogen) polymerisation during blood clotting can be affected strongly by LPS. The selectivity was indicated by the regularisation of clotting by lipopolysaccharide-binding protein (LBP). Since coagulopathies are a hallmark of T2D, we wondered whether they might too be caused by LPS (and reversed by LBP). We show here, using SEM and confocal microscopy, that platelet-poor-plasma from subjects with T2D had a much greater propensity for hypercoagulability and for amyloidogenesis, and that these could both be reversed by LBP. These data imply that coagulopathies are an important feature of T2D, and may be driven by ‘hidden’ LPS. Given the prevalence of amyloid formation in the sequelae of diabetes, this opens up novel strategies for both the prevention and treatment of T2D.

Selenoprotein S: a therapeutic target for diabetes and macroangiopathy?

Inflammatory response, oxidative stress, and endoplasmic reticulum (ER) stress are important pathophysiological bases of the occurrence and development of diabetes mellitus (DM) and macroangiopathy complications. Selenoprotein S (SELENOS) is involved in the regulation of these mechanisms; therefore, its association with DM and macroangiopathy has gradually received attention from scholars worldwide. SELENOS has different biological functions in different tissues and organs: it exerts antioxidant protection and has anti-ER stress effects in the pancreas and blood vessels, while it promotes the occurrence and development of insulin resistance in the liver, adipose tissue, and skeletal muscle. In addition, studies have confirmed that some SELENOS gene polymorphisms can influence the inflammatory response and are closely associated with the risk for developing DM and macroangiopathy. Therefore, comprehensive understanding of the association between SELENOS and inflammation, oxidative stress, and ER stress may better elucidate and supplement the pathogenic mechanisms of DM and macroangiopathy complications. Furthermore, in-depth investigation of the association of SELENOS function in different tissues and organs with DM and macroangiopathy may facilitate the development of new strategies for the prevention and treatment of DM and macrovascular complications. Here, we summarize the consensus and controversy regarding functions of SELENOS on currently available evidence.

Structure and Expression of Different Serum Amyloid A (SAA) Variants and their Concentration-Dependent Functions During Host Insults

Serum amyloid A (SAA) is, like C-reactive protein (CRP), an acute phase protein and can be used as a diagnostic, prognostic or therapy follow-up marker for many diseases. Increases in serum levels of SAA are triggered by physical insults to the host, including infection, trauma, inflammatory reactions and cancer. The order of magnitude of increase in SAA levels varies considerably, from a 10- to 100-fold during limited inflammatory events to a 1000-fold increase during severe bacterial infections and acute exacerbations of chronic inflammatory diseases. This broad response range is reflected by SAA gene duplications resulting in a cluster encoding several SAA variants and by multiple biological functions of SAA. SAA variants are single-domain proteins with simple structures and few post-translational modifications. SAA1 and SAA2 are inducible by inflammatory cytokines, whereas SAA4 is constitutively produced. We review here the regulated expression of SAA in normal and transformed cells and compare its serum levels in various disease states. At low concentrations (10-100 ng/ml), early in an inflammatory response, SAA induces chemokines or matrix degrading enzymes via Toll-like receptors and functions as an activator and chemoattractant through a G protein-coupled receptor. When an infectious or inflammatory stimulus persists, the liver continues to produce more SAA (> 1000 ng/ml) to become an antimicrobial agent by functioning as a direct opsonin of bacteria or by interference with virus infection of host cells. Thus, SAA regulates innate and adaptive immunity and this information may help to design better drugs to treat specific diseases.

Type 2 Diabetes in Young Females Results in Increased Serum Amyloid A and Changes to Features of High Density Lipoproteins in Both HDL2 and HDL3

Persons with type 2 diabetes mellitus (T2DM) have an elevated risk of atherosclerosis. High-density lipoproteins (HDL) normally protect against cardiovascular disease (CVD), but this may be attenuated by serum amyloid A (SAA). In a case-control study of young females, blood samples were compared between subjects with T2DM (n = 42) and individuals without T2DM (n = 42). SAA and apolipoprotein AI (apoAI) concentrations, paraoxonase-1 (PON-1), cholesteryl ester transfer protein (CETP), and lecithin-cholesterol acyltransferase (LCAT) activities were measured in the serum and/or HDL₂ and HDL₃ subfractions. SAA concentrations were higher in T2DM compared to controls: serum (30 mg/L (17, 68) versus 15 mg/L (7, 36); p = 0.002), HDL₂ (1.0 mg/L (0.6, 2.2) versus 0.4 mg/L (0.2, 0.7); p < 0.001), and HDL₃, (13 mg/L (8, 29) versus 6 mg/L (3, 13); p < 0.001). Serum-PON-1 activity was lower in T2DM compared to that in controls (38,245 U/L (7025) versus 41,109 U/L (5690); p = 0.043). CETP activity was higher in T2DM versus controls in HDL₂ (232.6 μmol/L (14.1) versus 217.1 μmol/L (25.1); p = 0.001) and HDL₃ (279.5 μmol/L (17.7) versus 245.2 μmol/L (41.2); p < 0.001). These results suggest that individuals with T2DM have increased SAA-related inflammation and dysfunctional HDL features. SAA may prove to be a useful biomarker in T2DM given its association with elevated CVD risk.

Epigenetic Signatures at AQP3 and SOCS3 Engage in Low-Grade Inflammation across Different Tissues

BACKGROUND

Elevated levels of C-reactive protein (CRP, determined by a high-sensitivity assay) indicate low-grade inflammation which is implicated in many age-related disorders. Epigenetic studies on CRP might discover molecular mechanisms underlying CRP regulation. We aimed to identify DNA methylation sites related to CRP concentrations in cells and tissues regulating low-grade inflammation.

RESULTS

Genome-wide DNA methylation was measured in peripheral blood in 1,741 participants of the KORA F4 study using Illumina HumanMethylation450 BeadChip arrays. Four CpG sites (located at BCL3, AQP3, SOCS3, and cg19821297 intergenic at chromosome 19p13.2, P ≤ 1.01E-07) were significantly hypomethylated at high CRP concentrations independent of various confounders including age, sex, BMI, smoking, and white blood cell composition. Findings were not sex-specific. CRP-related top genes were enriched in JAK/STAT pathways (Benjamini-Hochberg corrected P < 0.05). Results were followed-up in three studies using DNA from peripheral blood (EPICOR, n = 503) and adipose tissue (TwinsUK, n = 368) measured as described above and from liver tissue (LMU liver cohort, n = 286) measured by MALDI-TOF mass spectrometry using EpiTYPER. CpG sites at the AQP3 locus (significant p-values in peripheral blood = 1.72E-03 and liver tissue = 1.51E-03) and the SOCS3 locus (p-values in liver < 2.82E-05) were associated with CRP in the validation panels.

CONCLUSIONS

Epigenetic modifications seem to engage in low-grade inflammation, possibly via JAK/STAT mediated pathways. Results suggest a shared relevance across different tissues at the AQP3 locus and highlight a role of DNA methylation for CRP regulation at the SOCS3 locus.

Association of subclinical inflammation with deterioration of glycaemia before the diagnosis of type 2 diabetes: the KORA S4/F4 study

AIMS/HYPOTHESIS

The role of biomarkers of subclinical inflammation in the early deterioration of glycaemia before type 2 diabetes is largely unknown. We hypothesised that increased levels of circulating proinflammatory biomarkers and decreased circulating adiponectin would be associated with 7 year increases of HbA(1c) in non-diabetic individuals.

METHODS

This study was based on individuals who participated in the prospective Cooperative Health Research in the Region of Augsburg (KORA) S4 survey (1999-2001) and the 7 year follow-up KORA F4 (2006-2008) survey. Individuals with type 2 diabetes at baseline or with a diagnosis of diabetes in the period between both surveys were excluded, which left a sample of 850 men and women. Multivariable linear regression analyses were performed to assess associations among baseline values of leucocyte count and levels of acute-phase proteins (high-sensitivity C-reactive protein [hsCRP], serum amyloid A [SAA] and fibrinogen), IL-6 and adiponectin with changes in HbA1c between baseline and follow-up.

RESULTS

A high leucocyte count and high hsCRP, SAA and IL-6 levels were positively associated with changes in HbA(1c) after adjusting for age, sex, lifestyle factors and baseline HbA(1c). In contrast, the adiponectin level was inversely associated with changes in HbA(1c) (p value between <0.0001 and 0.020). The associations of leucocyte count and levels of hsCRP and SAA with HbA(1c) changes remained significant after additional adjustment for waist circumference and circulating lipids at baseline and for the 7 year change in waist circumference (p value between 0.004 and 0.045).

CONCLUSIONS/INTERPRETATION

An elevated leucocyte count and elevated hsCRP and SAA were associated with early deterioration of glycaemia before the diagnosis of type 2 diabetes. These associations were largely independent of baseline abdominal adiposity and increases in waist circumference.

Emerging functions of serum amyloid A in inflammation

SAA is a major acute-phase protein produced in large quantity during APR. The rise of SAA concentration in blood circulation during APR has been a clinical marker for active inflammation. In the past decade, research has been conducted to determine whether SAA plays an active role during inflammation and if so, how it influences the course of inflammation. These efforts have led to the discovery of cytokine-like activities of rhSAA, which is commercially available and widely used in most of the published studies. SAA activates multiple receptors, including the FPR2, the TLRs TLR2 and TLR4, the scavenger receptor SR-BI, and the ATP receptor P2X7. More recent studies have shown that SAA not only activates transcription factors, such as NF-κB, but also plays a role in epigenetic regulation through a MyD88-IRF4-Jmjd3 pathway. It is postulated that the activation of these pathways leads to induced expression of proinflammatory factors and a subset of proteins expressed by the M2 macrophages. These functional properties set SAA apart from well-characterized inflammatory factors, such as LPS and TNF-α, suggesting that it may play a homeostatic role during the course of inflammation. Ongoing and future studies are directed to addressing unresolved issues, including the difference between rSAA and native SAA isoforms and the exact functions of SAA in physiologic and pathologic settings.