Serum concentrations and expressions of serum amyloid A and leptin in adipose tissue are interrelated: the Genobin Study

Longitudinal proteomics of leptin treatment in humans with acute and chronic energy deficiency-induced hypoleptinemia reveal novel, mainly immune-related, pleiotropic effects

BACKGROUND

Leptin is known for its metabolic, immunomodulatory and neuroendocrine properties, but the full spectrum of molecules downstream of leptin and relevant underlying mechanisms remain to be fully clarified. Our objective was to identify proteins and pathways influenced by leptin through untargeted proteomics in two clinical trials involving leptin administration in lean individuals.

METHODS

We performed untargeted liquid chromatography-tandem mass spectrometry serum proteomics across two studies a) Short-term randomized controlled crossover study of lean male and female humans undergoing a 72-h fast with concurrent administration of either placebo or high-dose leptin; b) Long-term (36-week) randomized controlled trial of leptin replacement therapy in human females with acquired relative energy deficiency and hypoleptinemia. We explored longitudinal proteomic changes and run adjusted mixed models followed by post-hoc tests. We further attempted to identify ontological pathways modulated during each experimental condition and/or comparison, through integrated qualitative pathway and enrichment analyses. We also explored dynamic longitudinal relationships between the circulating proteome with clinical and hormonal outcomes.

RESULTS

289 and 357 unique proteins were identified per each respective study. Short-term leptin administration during fasting markedly upregulated several proinflammatory molecules, notably C-reactive protein (CRP) and cluster of differentiation (CD) 14, and downregulated lecithin cholesterol acyltransferase and several immunoglobulin variable chains, in contrast with placebo, which produced minimal changes. Quantitative pathway enrichment further indicated an upregulation of the acute phase response and downregulation of immunoglobulin- and B cell-mediated immunity by leptin. These changes were independent of participants' biological sex. In the long term study, leptin likewise robustly and persistently upregulated proteins of the acute phase response, and downregulated immunoglobulin-mediated immunity. Leptin also significantly and differentially affected a wide array of proteins related to immune function, defense response, coagulation, and inflammation compared with placebo. These changes were more notable at the 24-week visit, coinciding with the highest measured levels of serum leptin. We further identified distinct co-regulated clusters of proteins and clinical features during leptin administration indicating robust longitudinal correlations between the regulation of immunoglobulins, immune-related molecules, serpins (including cortisol and thyroxine-binding globulins), lipid transport molecules and growth factors, in contrast with placebo, which did not produce similar associations.

CONCLUSIONS

These high-throughput longitudinal results provide unique functional insights into leptin physiology, and pave the way for affinity-based proteomic analyses measuring several thousands of molecules, that will confirm these data and may fully delineate underlying mechanisms.

WISER Survivor Trial: Combined Effect of Exercise and Weight Loss Interventions on Adiponectin and Leptin Levels in Breast Cancer Survivors with Overweight or Obesity

Adipocyte dysregulation is one mechanism linking overweight and breast cancer recurrence. Exercise and weight loss are associated with a decreased risk of breast cancer recurrence in breast cancer survivors with overweight or obesity, which may be mediated through reduced leptin levels, increased adiponectin levels, and an elevated adiponectin to leptin (A:L) ratio. The four-arm randomized controlled WISER Survivor trial examined the 12-month intervention effects of exercise, weight loss, and the combination of exercise and weight loss on adipokine levels among breast cancer survivors (n = 339) with overweight or obesity. Compared with Control, the Combination of Exercise and Weight Loss decreased leptin levels (-35.9%; 95% CI: -46.8%, -25.0%) and increased A:L ratio (11.6%; 95% CI: 5.6%, 17.6%) but did not change adiponectin levels (4.1%; 95% CI: -3.1%, 11.2%). Compared with Control, Weight Loss Alone decreased leptin levels (-35.6%; 95% CI: -46.6%, -24.5%) and increased A:L ratio (10.6%; 95% CI: 4.7%, 16.5%) but did not change adiponectin levels (0.9%; 95% CI: -6.0%, 7.9%). Compared with Control, Exercise Alone did not change leptin levels, adiponectin levels, or A:L ratio. In analyses that consolidated intervention groups, compared with Control, weight loss of ≥5% decreased leptin levels (p trend < 0.01) and increased A:L ratio (p trend < 0.01) but did not alter adiponectin levels (p trend = 0.53). Weight loss, with or without exercise, was associated with decreased leptin levels in breast cancer survivors with overweight or obesity. Improvements in the adipokine secretion profile (A:L ratio) were primarily driven by a weight loss-induced change in leptin levels.

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.

Role of Paraoxonase1 in the Regulation of High-Density Lipoprotein Functionality and in Cardiovascular Protection

Significance: Human paraoxonase (PON) is a member of the gene family that includes paraoxonase 1 (PON1), PON2, and PON3. PON is known for its capacity to hydrolyze a wide range of substrates, including organophosphorus compounds, nerve gases, and aromatic carboxylic acid esters. Recent Advances: Several studies have highlighted the involvement of PON, particularly PON1, in the modulation of the capacity of high-density lipoprotein (HDL) to protect against the atherosclerosis process and its clinical manifestations. PON1 exhibits antioxidant and anti-inflammatory activities and may be involved in the regulation of the principal antiatherogenic activity of HDL, that is, the regulation of the reverse cholesterol transport process. Critical Issues: Although epidemiological studies have shown that there is an inverse relationship between HDL levels and cardiovascular risk, several studies have emphasized the importance of HDL functionality in protecting against cardiovascular diseases (CVD). Given that PON1 is involved in several atheroprotective functions of HDL, the aim of this article is to review the existing literature on PON1 and to discuss the principal mechanisms by which PON1 may exert its different activities. Future Directions: The elucidation of the mechanisms by which PON1 modulates the functionality of HDL as well as the identification of the interventions that stimulate PON1 activity and/or increase its plasma concentration would make it possible to propose new strategies to prevent CVD. Antioxid. Redox Signal. 34, 191-200.

Combination of Serum Amyloid A and C-Reactive Protein Exhibit Synergistic Effect in Angiogenesis by Inducing Inflammation and Vascular Network

The role of angiogenesis in tumor progression has been recognized as one of the hallmarks of cancer, but the mechanism of its action remains unclear. Inflammatory markers serum amyloid A (SAA) and C-reactive protein (CRP) are proposed to play causal roles in the development of various disorders, including malignancies. Previously, we identified the complex of CRP and SAA (CRP-SAA) with diagnostic and prognostic value better than either one of them in the serum of lung cancer patients. In this study, we further explored the stimulation function of CRP-SAA on angiogenesis and inflammation. To explore possible mechanisms, microarray datasets were downloaded from the Gene Expression Omnibus (GEO) database and multi-bioinformatics analysis revealed that THP-1 and human umbilical vein endothelial cells (HUVECs) responded to SAA stimulation with upregulation of two pro-angiogenic cytokines in common, i.e., C-X-C motif ligand 6 (CXCL6) and CXCL8, which were validated by subsequent experiments in vitro. CRP had weak effects as a single stimulus, but it can efficiently potentiate the SAA induction of cytokines, which was stronger than the sum of the both (P < 0.001). The synergistical effect of the combination of CRP and SAA enhanced HUVECs transwell and constricted morphology by upregulating the pro-angiogenic genes. These results indicated that the binding of CRP and SAA acted synergistically in pro-angiogenesis by increasing inflammation and inducing vascular network.

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.

Association between a urinary biomarker for exposure to PAH and blood level of the acute phase protein serum amyloid A in coke oven workers

BACKGROUND

Coke oven workers are exposed to both free and particle bound PAH. Through this exposure, the workers may be at increased risk of cardiovascular diseases. Systemic levels of acute phase response proteins have been linked to cardiovascular disease in epidemiological studies, suggesting it as a marker of these conditions. The aim of this study was to assess whether there was association between PAH exposure and the blood level of the acute phase inflammatory response marker serum amyloid A (SAA) in coke oven workers.

METHODS

A total of 87 male Polish coke oven workers from two different plants comprised the study population. Exposure was assessed by means of the individual post-shift urinary excretion of 1-hydroxypyrene, as internal dose of short-term PAH exposure, and by anti-benzo[a]pyrene diolepoxide (anti-B[a]PDE)-DNA), as a biomarker of long-term PAH exposure. Blood levels of acute phase proteins SAA and CRP were measured by immunoassay. C-reactive protein (CRP) levels were included to adjust for baseline levels of SAA.

RESULTS

Multiple linear regression showed that the major determinants of increased SAA levels were urinary 1-hydroxypyrene (beta = 0.56, p = 0.030) and serum CRP levels (beta = 7.08; p < 0.0001) whereas anti-B[a]PDE-DNA, the GSTM1 detoxifying genotype, diet, and smoking were not associated with SAA levels.

CONCLUSIONS

Urinary 1-hydroxypyrene as biomarker of short-term PAH exposure and serum levels of CRP were predictive of serum levels of SAA in coke oven workers. Our data suggest that exposure of coke oven workers to PAH can lead to increased systemic acute response and therefore potentially increased risk of cardiovascular disease.

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.

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.

The differential plasma proteome of obese and overweight individuals undergoing a nutritional weight loss and maintenance intervention

PURPOSE

The nutritional intervention program "DiOGenes" focuses on how obesity can be prevented and treated from a dietary perspective. We generated differential plasma proteome profiles in the DiOGenes cohort to identify proteins associated with weight loss and maintenance and explore their relation to body mass index, fat mass, insulin resistance, and sensitivity.

EXPERIMENTAL DESIGN

Relative protein quantification was obtained at baseline and after combined weight loss/maintenance phases using isobaric tagging and MS/MS. A Welch t-test determined proteins differentially present after intervention. Protein relationships with clinical variables were explored using univariate linear models, considering collection center, gender and age as confounding factors.

RESULTS

Four hundred and seventy three subjects were measured at baseline and end of the intervention; 39 proteins were longitudinally differential. Proteins with largest changes were sex hormone-binding globulin, adiponectin, C-reactive protein, calprotectin, serum amyloid A, and proteoglycan 4 (PRG4), whose association with obesity and weight loss is known. We identified new putative biomarkers for weight loss/maintenance. Correlation between PRG4 and proline-rich acidic protein 1 variation and Matsuda insulin sensitivity increment was showed.

CONCLUSION AND CLINICAL RELEVANCE

MS-based proteomic analysis of a large cohort of non-diabetic overweight and obese individuals concomitantly identified known and novel proteins associated with weight loss and maintenance.

Factors associated with adipocyte size reduction after weight loss interventions for overweight and obesity: a systematic review and meta-regression

AIMS

Enlarged adipocytes are a prime feature of adipose tissue dysfunction, and may be an appropriate target to decrease disease risk in obesity. We aimed to assess the change in adipocyte size in response to lifestyle and surgical weight loss interventions for overweight or obesity; and to explore whether certain participant and intervention characteristics influence this response.

METHODS

We systematically searched MEDLINE, EMBASE, CINAHL and Cochrane electronic databases to identify weight loss studies that quantified adipocyte size before and after the intervention. Using meta-regression analysis, we assessed the independent effects of weight loss, age, sex, adipocyte region, and intervention type (surgical vs. lifestyle) on adipocyte size reduction. We repeated the model as a sensitivity analysis including only the lifestyle interventions.

RESULTS

Thirty-five studies met our eligibility criteria. In our main model, every 1.0% weight loss was associated with a 0.64% reduction in adipocyte size (p=0.003); and adipocytes from the upper body decreased 5% more in size than those in the lower body (p=0.009). These relationships were no longer significant when focusing only on lifestyle interventions. Moreover, age, sex and intervention type did not independently affect adipocyte size reduction in either model.

CONCLUSIONS

Weight loss in obese individuals is consistently associated with a decrease in adipocyte size that is more pronounced in upper-body adipocytes. It remains to be clarified how biological differences and intervention characteristics influence this relationship, and whether it corresponds with reductions in other aspects of adipose tissue dysfunction and disease risk.

Decrease of circulating SAA is correlated with reduction of abdominal SAA secretion during weight loss

OBJECTIVE

The study goal was to determine the effect of weight loss (WL) alone and with aerobic exercise (WL + AEX) on serum amyloid A (SAA) levels and adipose SAA secretion from gluteal and abdominal depots.

METHODS

Ninety-six overweight or obese postmenopausal women undertook a 6-month WL alone (n = 47) or with AEX training (n = 49) (6 months WL and WL + AEX are considered WL when groups were combined). Their serum SAA levels, body weight, and adipose SAA secretion ex vivo from gluteal and abdominal depot were measured before and after WL interventions.

RESULTS

The participants lost an average of 8% body weight with a 10% decrease of serum SAA. Serum SAA levels remained significantly correlated with body weight before and after WL. However, the changes of serum SAA level did not correlate with changes of body weight. The gluteal adipose tissue secreted ∼50% more SAA than the abdominal tissue, but the changes of abdominal, but not gluteal, SAA secretion correlated (R(2) = 0.19, p < 0.01) with those of serum SAA levels during WL.

CONCLUSIONS

No linear correlation between the decrease in systemic SAA and WL was found. There is a depot-dependent difference in adipose SAA secretion and abdominal SAA secretion, which may partially account for the systemic SAA reduction during WL.

Effect of serum amyloid A1 treatment on global gene expression in THP-1-derived macrophages

OBJECTIVE

To investigate the effect of serum amyloid A1 (SAA1) on global gene expression in macrophages derived from THP-1 monocytes.

MATERIALS AND METHODS

Global genetic expression in THP-1-derived macrophages was determined using Illumina HT-12 microarray chips and the results were validated by real-time PCR. Cytokine levels in cellular supernatant were quantified by ELISA.

RESULTS

In total, 55 genes were upregulated with fold difference greater than two when THP-1-derived macrophages were incubated with SAA1 for 8 h. SAA1 is a strong cytokine inducer with significant upregulation of chemokines CCL1, CCL3, and CCL4 and this was confirmed by both real-time PCR and ELISA quantification. SAA1 also promotes the upregulation of genes involved in phagocytosis, anti-apoptosis, and tissue remodeling.

CONCLUSIONS

SAA1 appears to play an important role during the immune response and in chronic inflammatory diseases through the stimulation of genes involved in cytokine production, phagocytosis, and anti-apoptosis.

Relationship between osteoporosis and adipose tissue leptin and osteoprotegerin in patients with chronic obstructive pulmonary disease

INTRODUCTION

The role of fat-bone interactions in the pathogenesis of osteoporosis in chronic obstructive pulmonary disease (COPD) is poorly understood. Our aim was to investigate expressions of leptin and osteoprotegerin (OPG) in the adipose tissue, and their relationships to osteoporosis in patients with COPD.

METHODS

In 39 patients with stable COPD, bone mineral density (BMD) and body composition was assessed by Dual Energy X-Ray Absorptiometry. Serum leptin was determined by the enzyme-linked immunosorbent assay, and bone turnover markers osteocalcin and β-crosslaps by the electrochemiluminiscence immunoassays. Subcutaneous adipose tissue samples were analyzed using real-time PCR.

RESULTS

Twenty-one patients without, and 18 with osteoporosis were enrolled (35 men; age 62.2 ± 7.3years). Compared to patients without osteoporosis, those with the disease had significantly lower serum levels and adipose tissue expressions of leptin, in association with increased serum β-crosslaps (p=0.028, p=0.034, p=0.022, respectively). Log adipose tissue leptin was inversely related to serum β-crosslaps (p=0.015), and directly to serum leptin (p<0.001) and to the total, femoral, and lumbar BMD and T-score (p<0.02 for all relationships). Adipose tissue OPG expression was related to all variables of bone density except for lumbar BMD and T-score (p<0.05 for all relationships). Log adipose tissue leptin and OPG expressions predicted femoral T-score independently of age, gender and pulmonary function (p<0.001, adjusted R(2)=0.383; p=0.008, adjusted R(2)=0.301, respectively). Introducing body mass (or fat mass) index into these models eliminated independent predictive value of leptin and OPG expressions.

CONCLUSION

Our results suggest that adipose tissue leptin and OPG expressions are related to osteoporosis in patients with COPD, and appear to act as mediators between fat mass and BMD.

Genome-wide association study identifies two novel regions at 11p15.5-p13 and 1p31 with major impact on acute-phase serum amyloid A

Elevated levels of acute-phase serum amyloid A (A-SAA) cause amyloidosis and are a risk factor for atherosclerosis and its clinical complications, type 2 diabetes, as well as various malignancies. To investigate the genetic basis of A-SAA levels, we conducted the first genome-wide association study on baseline A-SAA concentrations in three population-based studies (KORA, TwinsUK, Sorbs) and one prospective case cohort study (LURIC), including a total of 4,212 participants of European descent, and identified two novel genetic susceptibility regions at 11p15.5-p13 and 1p31. The region at 11p15.5-p13 (rs4150642; p = 3.20×10⁻¹¹¹) contains serum amyloid A1 (SAA1) and the adjacent general transcription factor 2 H1 (GTF2H1), Hermansky-Pudlak Syndrome 5 (HPS5), lactate dehydrogenase A (LDHA), and lactate dehydrogenase C (LDHC). This region explains 10.84% of the total variation of A-SAA levels in our data, which makes up 18.37% of the total estimated heritability. The second region encloses the leptin receptor (LEPR) gene at 1p31 (rs12753193; p = 1.22×10⁻¹¹) and has been found to be associated with CRP and fibrinogen in previous studies. Our findings demonstrate a key role of the 11p15.5-p13 region in the regulation of baseline A-SAA levels and provide confirmative evidence of the importance of the 1p31 region for inflammatory processes and the close interplay between A-SAA, leptin, and other acute-phase proteins.

An elevated level of acute-phase serum amyloid A (A-SAA), a sensitive marker of the acute inflammatory state with high heritability estimates, causes amyloidosis and is a risk factor for atherosclerosis and its clinical complications, type 2 diabetes, as well as various malignancies. This study describes the first genome-wide association study on baseline A-SAA concentrations. In a meta-analysis of four genome-wide scans totalling 4,212 participants of European descent, we identified two novel genetic susceptibility regions on chromosomes 11 and 1 to be associated with baseline A-SAA concentrations. The chromosome 11 region contains the serum amyloid A1 gene and the adjacent genes and explains a high percentage of the total estimated heritability. The chromosome 1 region is a known genetic susceptibility region for inflammation. Taken together, we identified one region, which seems to be of key importance in the regulation of A-SAA levels and represents a novel potential target for the investigation of related clinical entities. In addition, our findings indicate a close interplay between A-SAA and other inflammatory proteins, as well as a larger role of a known genetic susceptibility region for inflammatory processes as it has been assumed in the past.

Interaction of adenosine 3',5'-cyclic monophosphate and tumor necrosis factor-alpha on serum amyloid A3 expression in mouse granulosa cells: dependence on CCAAT-enhancing binding protein-beta isoform

TNFalpha is an inflammatory-related cytokine that has inhibitory effects on gonadotropin- and cAMP-stimulated steroidogenesis and folliculogenesis. Because ovulation is an inflammatory reaction and TNF specifically induces serum amyloid A3 (SAA3) in mouse granulosa cells, the effect of cAMP on TNF-induced SAA3 promoter activity, mRNA and protein was investigated. Granulosa cells from immature mice were cultured with TNF and/or cAMP. TNF increased SAA3 promoter activity, mRNA, and protein, which were further increased by cAMP. cAMP alone increased SAA3 promoter activity, but SAA3 mRNA and protein remained undetectable. Thus, there appeared to be different mechanisms by which TNF and cAMP regulated SAA3 expression. SAA3 promoters lacking a nuclear factor (NF)-kappaB-like site or containing its mutant were not responsive to TNF but were responsive to cAMP. Among four CCAAT-enhancing binding protein (C/EBP) sites in the SAA3 promoter, the C/EBP site nearest the NF-kappaB-like site was required for TNF-induced SAA3. The C/EBP site at -75/-67 was necessary for responsiveness to cAMP. Dominant-negative C/EBP and cAMP response element-binding protein or short interfering RNA of C/EBPbeta blocked TNF- or cAMP-induced SAA3 promoter activity. The combination of TNF and cAMP increased C/EBPbeta protein above that induced by TNF or cAMP alone. Thus, cAMP in combination with TNF specifically induced C/EBPbeta protein, leading to enhanced SAA3 expression but requiring NF-kappaB in mouse granulose cells. In addition, like TNF, SAA inhibited cAMP-induced estradiol accumulation and CYP19 levels. These data indicate SAA may play a role in events occurring during the ovulation process.

Adipokines and dietary interventions in human obesity

Obesity is a multisystem disorder associated with cardiovascular and metabolic complications. According to recent studies, it is characterized as a condition of low-grade inflammation with altered adipose tissue function and secretion of various adipokines. One of the strategies in obesity treatment is dietary intervention (DI) that could modulate cytokine levels in a favourable way. The aim of this review was to summarize the results of studies performed in the last 13 years investigating DI programmes accompanied with weight loss in relation to profile of adipokines at different level (adipose tissue mRNA, adipose tissue secretion and circulating level) and identify whether modulations of adipokines are implicated in the positive effects of DIs. The overall finding is that DIs leading to 5-10% weight loss modulate production of certain adipokines and generally induce improvement of clinical parameters, e.g. insulin sensitivity, but the amelioration of obesity complications is not coherent with the pattern of adipokine regulation, except maybe for leptin. Global analysis of the adipose tissue secretome and measurement of panels of adipokines may prove more informative than studies on individual molecules.

Release of 12 adipokines by adipose tissue, nonfat cells, and fat cells from obese women

The relative release in vitro of endothelin-1, zinc-alpha2-glycoprotein (ZAG), lipocalin-2, CD14, RANTES (regulated on activation, normal T cell expressed and secreted protein), lipoprotein lipase (LPL), osteoprotegerin (OPG), fatty acid-binding protein 4 (FABP-4), visfatin/PBEF/Nampt, glutathione peroxidase-3 (GPX-3), intracellular cell adhesion molecule 1 (ICAM-1), and amyloid A was examined using explants of human adipose tissue as well as the nonfat cell fractions and adipocytes from obese women. Over a 48-h incubation the majority of the release of LPL was by fat cells whereas that of lipocalin-2, RANTES, and ICAM-1 was by the nonfat cells present in human adipose tissue. In contrast appreciable amounts of OPG, amyloid A, ZAG, FABP-4, GPX-3, CD14, and visfatin/PBEF/Nampt were released by both fat cells and nonfat cells. There was an excellent correlation (r = 0.75) between the ratios of adipokine release by fat cells to nonfat cells over 48 h and the ratio of their mRNAs in fat cells to nonfat cells at the start of the incubation. The total release of ZAG, OPG, RANTES, and amyloid A by incubated adipose tissue explants from women with a fat mass of 65 kg was not different from that by women with a fat mass of 29 kg. In contrast that of ICAM-1, FABP-4, GPX-3, visfatin/PBEF/Nampt, CD14, lipocalin-2, LP, and endothelin-1 was significantly greater in tissue from women with a total fat mass of 65 kg.

Association between serum amyloid A and obesity: a meta-analysis and systematic review

BACKGROUND

Emerging evidence indicates an association of the acute-phase protein serum amyloid A (SAA) with obesity. Here we review and summarize quantitatively the available data related to this association.

METHODS

PubMed was systematically searched using the terms "serum amyloid A" and "obesity." Eighty-one relevant studies between January 1966 and July 2009 were identified. Of these, only 11 cross-sectional studies and 10 prospective studies with successful interventions met our inclusion criteria for the meta-analysis. All analyses were conducted using the Comprehensive Meta-Analysis software. Literature pertaining to the relationship between SAA and other inflammatory markers, and the association between SAA and obesity-related disorders, such as cardiovascular diseases, atherosclerosis, diabetes, and insulin resistance was also reviewed.

RESULTS

A strong association between body mass index and SAA levels was found in the 11 cross-sectional studies. The overall correlation coefficient is 0.230 (95% CI 0.160-0.297, P < 0.0005). The ten prospective studies were subsequently analyzed, and the difference in SAA levels before and after weight loss, expressed as standardized mean difference was -0.480 (95% CI -0.678 to -0.283, P < 0.0005). We discuss some potential underlying mechanisms and clinical applications for reducing SAA levels in obesity.

Association of serum amyloid A levels with adipocyte size and serum levels of adipokines: differences between men and women

The aim of this study was to characterize the association between adipocyte enlargement and circulating levels of serum amyloid A (SAA). Furthermore, we wanted to search for possible associations with measures of glycemic control and levels of circulating adipokines and/or inflammatory markers in men and women with a large range in body mass index. The study cohort consisted of 167 subjects, 114 non-diabetic and 53 with Type 2 diabetes. Adipocyte diameter as well as circulating levels of SAA, C-reactive protein (CRP), adiponectin, leptin, interleukin-6, tumor necrosis factor alpha, glucose and insulin were measured. Women had higher serum levels of SAA than men (p=0.044). SAA levels were weakly but positively correlated with BMI (p=0.043) and % body fat (p=0.027) in all subjects as well as subcutaneous adipocyte diameter (p=0.034) in women. Furthermore, in all subjects we found correlations between SAA levels and levels of CRP (p<0.001), interleukin-6 (p<0.001), leptin (p=0.003), insulin (p=0.006), HbA1c (p=0.02) and HOMA-IR (p=0.002). A majority of the correlations were strongest in women. In conclusion, serum levels of SAA are strongly correlated with serum levels of inflammatory markers as well as measures of glycemic control. There seems to be large sex differences in these associations suggesting that sex-specific factors need to be considered when analyzing SAA levels in relation to metabolic disease.

Serum amyloid A is independently associated with metabolic risk factors but not with early atherosclerosis: the Cardiovascular Risk in Young Finns Study

BACKGROUND

Serum amyloid A (SAA) is a sensitive marker of inflammation and its elevation has been implicated in obesity and in cardiovascular disease, yet data on its regulation in young adults or on its role in early atherosclerosis is scarce. We investigated which factors explain the variation in SAA and analysed whether SAA could be associated with preclinical atherosclerosis.

METHODS

Serum amyloid A levels were measured in participants of the Cardiovascular Risk in Young Finns Study (n = 2280, n = 1254 women, n = 1026 men). Correlates and determinants of SAA were analysed and the effect of SAA on subclinical atherosclerosis, measured as intima-media thickness (IMT) and carotid artery compliance, was evaluated with risk-factor adjusted models.

RESULTS

Serum amyloid A correlated directly and independently of BMI with C-reactive protein (CRP), waist circumference and leptin in both sexes, with total cholesterol, LDL cholesterol and ApolipoproteinA1 (ApoA1) in women and with triglycerides, insulin levels and insulin resistance in men. Use of combined oral contraceptives and intrauterine device was also associated with SAA levels. Determinants for SAA included CRP, leptin and ApoA1 in women, and CRP, leptin and HDL cholesterol in men. SAA levels correlated with carotid compliance in both sexes and with IMT in men, yet SAA had no independent effect on IMT or carotid compliance in multivariable analysis.

CONCLUSIONS

Serum amyloid A was associated with several metabolic risk factors but was not an independent predictor of IMT or carotid artery compliance. Further longitudinal studies will show whether SAA holds a prognostic value as a risk marker, analogously to CRP.

In uteroand postnatal exposure to a high-protein or high-carbohydrate diet leads to differences in adipose tissue mRNA expression and blood metabolites in kittens

The objective of the present study was to measure the differences in body composition, adipose tissue gene expression, blood metabolite and hormone concentrations, and insulin sensitivity in kittens exposed to high-protein (HP) or high-carbohydrate (HC) nutritionin uteroand through the growth period. Eight dams were randomised onto two test diets, and fed the diets throughout gestation and lactation. Male offspring were evaluated for 9 months. Kittens were weaned at 2 months of age onto the same treatment diet as the dam and were allowed to consume dietsad libitum. The HC diet contained 34·3 % crude protein (CP), 19·2 % fat and 30·8 % digestible carbohydrate, while the HP diet contained 52·9 % CP, 23·5 % fat and 10·8 % digestible carbohydrate. Blood samples were collected at 6 months after birth. Body composition was determined at 2 and 8 months of age and an intravenous glucose tolerance test, neutering and adipose tissue biopsy conducted at 8 months of age. Physical activity was quantified at 6 and 9 months. Energy intake, DM intake and body weight were not different between groups. At 2 months, blood TAG were greater (P < 0·05) in kittens fed the HP diet. At 8 months, blood leptin was higher (P < 0·05) in kittens fed the HC diet, while chemokine receptor 5, hormone-sensitive lipase, uncoupling protein 2, leptin and insulin receptor mRNA were greater (P < 0·05) in kittens fed the HP diet. The present results demonstrate some of the changes in blood metabolites and hormones, physical activity and mRNA abundance that occur with feeding high protein levels to kittens.