Sfrp5 correlates with insulin resistance and oxidative stress

Prognostic significance of serum secreted frizzled-related protein 5 in patients with acute aortic dissection

Background

Secreted frizzled-related protein 5 (SFRP5) is a novel adipokine that has been found to be closely associated with metabolic and cardiovascular diseases. We investigated serum SFRP5 levels during the acute phase and their predictive value for the prognosis of acute aortic dissection (AAD).

Methods

In total, 152 AAD patients and 164 controls were enrolled in this study. Serum SFRP5 levels were measured using an enzyme-linked immunosorbent assay (ELISA). AAD patients were divided into high-SFRP5 and low-SFRP5 groups based on the optimal cutoff value and followed up for prognosis. The primary endpoint was all-cause mortality, and the secondary endpoint focused on AAD-related events (including AAD-related mortality and unplanned reoperations).

Results

Serum SFRP5 levels were significantly higher in AAD patients than in non-AAD controls, regardless of whether they had Stanford type A or B AD. Multivariate logistic regression analysis revealed an independent association between SFRP5 and the presence of AAD (adjusted OR 1.267, 95 % CI 1.152-1.394; p < 0.001). The receiver operating characteristic curve demonstrated that the optimal cutoff value for SFRP5 to predict the presence of AAD was 10.26 ng/mL (AUC 0.7241, sensitivity 49.34 %, specificity 87.20 %). Notably, serum SFRP5 levels of patients in the death group were significantly higher than those in the survival group. Compared with patients in the low-SFRP5 group, those in the high-SFRP5 group exhibited a significantly increased risk of all-cause mortality (HR 9.540, 95 % CI 2.803-32.473; p < 0.001) and AAD-related events (HR 6.915, 95 % CI 2.361-20.254; p < 0.001) during the follow-up period.

Conclusion

Serum SFRP5 levels were significantly elevated in the acute phase of AAD, and high serum SFRP5 levels were independently associated with poor AAD prognosis. These results suggest that serum SFRP5 level during the acute phase may be an effective biomarker and therapeutic target for the prognosis of AAD.

Secreted frizzled-related protein 5 overexpression reverses oxLDL-induced lipid accumulation in human vascular smooth muscle cells

Atherosclerosis (AS) is the major cause of multiple cardiovascular diseases. In addition, the lipid accumulation of human vascular smooth muscle cells (HVSMCs) can cause the occurrence of AS. Secreted frizzled-related protein 5 (Sfrp5) was known to be downregulated in AS; however, the detailed function of Sfrp5 in HVSMCs remains unclear. Specifically, we found that Sfrp5 expression in oxLDL-treated HVSMCs was downregulated. Sfrp5 overexpression inhibited the viability of HVSMCs induced by oxLDL. In addition, oxLDL-induced proliferation and migration in HVSMCs were abolished by Sfrp5 overexpression. Sfrp5 overexpression reduced oxLDL-caused oxidative stress, lipid accumulation, and inflammation in HVSMCs. Meanwhile, oxLDL treatment increased the expressions of Wnt5a, c-Myc, and β-catenin in HVSMCs, while this phenomenon was rescued by Sfrp5 overexpression. Furthermore, the inhibitory effect of Sfrp5 upregulation on the viability and migration of HVSMCs was reversed by R-spondin 1. These results indicate that Sfrp5 overexpression could reverse oxLDL-induced lipid accumulation in HVSMCs through inactivating Wnt5a/β-catenin signaling pathway.

Follicular fluid composition and reproductive outcomes of women with polycystic ovary syndrome undergoing in vitro fertilization: A systematic review

Polycystic ovary syndrome (PCOS) is recognized as one of the most prevalent endocrinopathy in women at reproductive age. As affected women tend to have poorer assisted reproductive technology (ART) outcomes, PCOS has been suggested to endanger oocyte quality and competence development. The aim of this systematic review was to summarize the available evidence on how the follicular fluid (FF) profile of women with PCOS undergoing in vitro fertilization (IVF) treatment differs from the FF of normo-ovulatory women. For that, an electronic search in PubMed and Web of Science databases was conducted (up to December 2021). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses - PRISMA guidelines were followed, and the Newcastle-Ottawa Scale was used to assess the risk of bias in the included studies. Data retrieved from papers included (n=42), revealed that the FF composition of women with PCOS compared to those without PCOS predominantly diverged at the following molecular classes: oxidative stress, inflammatory biomarkers, growth factors and hormones. Among those biomarkers, some were proposed as being closely related to pathophysiological processes, strengthening the hypothesis that low-grade inflammation and oxidative stress play a critical role in the pathogenesis of PCOS. Notwithstanding, it should be noticed that the available data on PCOS FF fingerprints derives from a limited number of studies conducted in a relatively small number of subjects. Furthermore, phenotypic heterogeneity of PCOS hampers wider comparisons and weakens putative conclusions. Therefore, future studies should be focused at comparing well characterized patient subgroups according to phenotypes.

Secreted frizzled-related protein 5: A promising therapeutic target for metabolic diseases via regulation of Wnt signaling

Metabolic diseases pose a significant global health challenge, characterized by an imbalance in metabolism and resulting in various complications. Secreted frizzled-related protein 5 (SFRP5), an adipokine known for its anti-inflammatory properties, has gained attention as a promising therapeutic target for metabolic diseases. SFRP5 acts as a key regulator in the Wnt signaling pathway, exerting its influence on critical cellular functions including proliferation, differentiation, and migration. Its significance extends to the realm of adipose tissue biology, where it plays a central role in regulating inflammation, insulin resistance, adipogenesis, lipid metabolism, glucose homeostasis, and energy balance. By inhibiting Wnt signaling, SFRP5 facilitates adipocyte growth, promotes lipid accumulation, and contributes to a decrease in oxidative metabolism. Lifestyle interventions and pharmacological treatments have shown promise in increasing SFRP5 levels and protecting against metabolic abnormalities. SFRP5 is a pivotal player in metabolic diseases and presents itself as a promising therapeutic target. An overview of SFRP5 and its involvement in metabolic disorders and metabolism is provided in this comprehensive review. By elucidating these aspects, valuable insights can be gained to foster the development of effective strategies in combating metabolic diseases.

PPAR-γ signaling in nonalcoholic fatty liver disease: Pathogenesis and therapeutic targets

Non-alcoholic fatty liver disease (NAFLD), currently the leading cause of global chronic liver disease, has emerged as a major public health problem, more efficient therapeutics of which are thus urgently needed. Peroxisome proliferator-activated receptor γ (PPAR-γ), ligand-activated transcription factors of the nuclear hormone receptor superfamily, is considered a crucial metabolic regulator of hepatic lipid metabolism and inflammation. The role of PPAR-γ in the pathogenesis of NAFLD is gradually being recognized. Here, we outline the involvement of PPAR-γ in the pathogenesis of NAFLD through adipogenesis, insulin resistance, inflammation, oxidative stress, endoplasmic reticulum stress, and fibrosis. In addition, the evidence for PPAR-γ- targeted therapy for NAFLD are summarized. Altogether, PPAR-γ is a promising therapeutic target for NAFLD, and the development of drugs that can balance the beneficial and undesirable effects of PPAR-γ will bring new light to NAFLD patients.

Assesement of serum Sfrp5/Wnt-5a level and its utility in the risk stratification of treatment naïve patients with metabolic syndrome

Our study focused on investigating the clinical significance of serum Sfrp5/Wnt-5a levels as a risk marker in metabolic syndrome (MetS). The study involved a total of 107 treatment-naive MetS cases and 100 controls with similar age and sex belonging to northern India. The profiling of clinical, biochemical, and anthropometric variables was done. ELISA methods were employed for serum cytokine estimation. Serum Sfrp5 was inversely correlated with BMI, WC, SBP, DBP, FPG, TG, fasting insulin level, and HOMA-IR in both males and females. The best cutoff value for Sfrp5 to predict MetS in males was ≤40.48 ng/ml (sensitivity 53.70% and specificity 90.48%), while in female, it was ≤66.67 ng/ml (sensitivity 98.11% and specificity 34.48%). MetS occurrence decreased with increasing concentration of Sfrp5 with an odds ratio (OR) of 0.95 (95% CI = 0.92-0.98, P < .001) in male and 0.93 (95% CI = 0.91-0.97, P < .001) in female. Quartile analysis revealed that odds of MetS significantly decreased in quartile 4 vs. 1, 0.06 (95% CI = 0.01-0.25), P = .001 and 0.13 (95% CI = 0.04-0.44), P = .001, respectively, in male and female. The inverse association of serum concentration of Sfrp5 with MetS might have a useful addition to the available risk marker as well as a therapeutic target for MetS.

Pancreatic Islets as a Target of Adipokines

Rising rates of obesity are intricately tied to the type 2 diabetes epidemic. The adipose tissues can play a central role in protection against or triggering metabolic diseases through the secretion of adipokines. Many adipokines may improve peripheral insulin sensitivity through a variety of mechanisms, thereby indirectly reducing the strain on beta cells and thus improving their viability and functionality. Such effects will not be the focus of this article. Rather, we will focus on adipocyte-secreted molecules that have a direct effect on pancreatic islets. By their nature, adipokines represent potential druggable targets that can reach the islets and improve beta-cell function or preserve beta cells in the face of metabolic stress. © 2022 American Physiological Society. Compr Physiol 12:1-27, 2022.

Secreted frizzled-related protein 5 promotes angiogenesis of human umbilical vein endothelial cells and alleviates myocardial injury in diabetic mice with myocardial infarction by inhibiting Wnt5a/JNK signaling

The purpose of this study is to investigate whether secreted frizzled-related protein 5 (SFRP5) affects the proliferation, migration and angiogenesis of human umbilical vein endothelial cells (HUVECs) induced by high glucose (HG). HUVECs were treated with different concentrations of glucose. MTT, wound healing, angiogenesis, and ELISA assays were used to detect cell cytotoxicity, migration, tube formation, and VEGF165 and VEGF165b levels, respectively. The mice model of type 2 diabetes mellitus (T2DM) complicated with myocardial infarction (MI) was established. SFRP5 was injected intrabitoneally for 2 weeks. cardiac output (CO), left ventricular ejection fraction (LVEF) and left ventricular shortening fraction (LVSF) were detected by echocardiography. Western blot was used to detect the protein levels of SFRP5, Wnt5a, JNK1/2/3, p-JNK1/2/3, TGF-β1, Caspase3, Bax, and Bcl-2. The expression of SFRP5 was declined in HG-induced HUVECs and T2DM-MI. Intervention of SFRP5 promoted the migration of HUVECs and angiogenesis, as evidenced by a lower expression of Bax and caspase3, but a higher expression of Bcl-2. Meanwhile, SFRP5 inhibition repress Wnt5a and p-JNK expression. Howerver, The JNK inhibitor (SP600125) enhanced the down-regulation of Wnt5a/JNK pathway proteins by SFRP5. SFRP5 intervention increased the levels of CO, LVSF, and LVEF in T2DM-MI mice. SFRP5 inhibited myocardial pathological injury and fibrosis in T2DM-MI mice and SFRP5 could down-regulate Wnt5a and p-JNK1/2/3 activation. SFRP5 promotes the proliferation, migration and angiogenesis of HUVECs induced by HG, and inhibits cardiac dysfunction, pathological damage, fibrosis, and myocardial angiogenesis in diabetic myocardial ischemia mice, which is achieved by inhibiting Wnt5a/JNK signaling.

Exercise training modulates adipokine dysregulations in metabolic syndrome

Metabolic syndrome (MetS) is a cluster of risk factors for various metabolic diseases, and it is characterized by central obesity, dyslipidemia, hypertension, and insulin resistance. The core component for MetS is adipose tissue, which releases adipokines and influences physical health. Adipokines consist of pro and anti-inflammatory cytokines and contribute to various physiological functions. Generally, a sedentary lifestyle promotes fat accumulation and secretion of pro-inflammatory adipokines. However, regular exercise has been known to exert various beneficial effects on metabolic and cognitive disorders. Although the mechanisms underlying exercise beneficial effects in MetS are not fully understood, changes in energy expenditure, fat accumulation, circulatory level of myokines, and adipokines might be involved. This review article focuses on some of the selected adipokines in MetS, and their responses to exercise training considering possible mechanisms.

Serum secreted frizzled-related protein 5 in relation to insulin sensitivity and its regulation by insulin and free fatty acids

PURPOSE

Secreted frizzled-related protein 5 (SFRP5) is an adipokine, which acts as an inhibitor of noncanonical WNT signaling pathway. It has been suggested to exert anti-inflammatory and insulin-sensitizing effects, however, contradictory data has also been reported. The aim of this study was to assess serum SFRP5 concentration in a young healthy population in relation to insulin sensitivity and its regulation by hyperinsulinemia and/or serum free fatty acids (FFA) elevation.

METHODS

We examined 150 healthy subjects (83 normal-weight and 67 overweight/obese). Insulin sensitivity (M) was measured with hyperinsulinemic-euglycemic clamp. In 20 male subjects, clamp was prolonged to 6 h and after 1 week another clamp with the concurrent Intralipid/heparin infusion was performed. Independent group of 10 male subjects received infusions of Intralipid/heparin or saline in 1-week interval.

RESULTS

Baseline SFRP5 was lower in the overweight/obese group (p = 0.01) and was positively associated with M (r = 0.23, p = 0.006) and serum adiponectin (r = 0.55, p < 0.001) and negatively with BMI (r = -0.18, p = 0.03). In multiple regression analysis, adiponectin was independently associated with SFRP5. Insulin infusion resulted in a decrease in serum SFRP5, both at 120' (p = 0.02) and 360' (p = 0.031). This effect was not observed during the clamp with Intralipid/heparin as well as during Intralipid/heparin alone or saline infusions.

CONCLUSIONS

The relation between SFRP5 and insulin sensitivity is mainly dependent on adiponectin. FFA abolish a decrease in circulating SFRP5 caused by insulin, but Intralipid/heparin infusion alone does not regulate SFRP5 concentration. Insulin seems to be more important factor in the regulation of circulating SFRP5 levels than FFA.

Adipokines: New Potential Therapeutic Target for Obesity and Metabolic, Rheumatic, and Cardiovascular Diseases

Besides its role as an energy storage organ, adipose tissue can be viewed as a dynamic and complex endocrine organ, which produces and secretes several adipokines, including hormones, cytokines, extracellular matrix (ECM) proteins, and growth and vasoactive factors. A wide body of evidence showed that adipokines play a critical role in various biological and physiological functions, among which feeding modulation, inflammatory and immune function, glucose and lipid metabolism, and blood pressure control. The aim of this review is to summarize the effects of several adipokines, including leptin, diponectin, resistin, chemerin, lipocalin-2 (LCN2), vaspin, omentin, follistatin-like 1 (FSTL1), secreted protein acidic and rich in cysteine (SPARC), secreted frizzled-related protein 5 (SFRP5), C1q/TNF-related proteins (CTRPs), family with sequence similarity to 19 member A5 (FAM19A5), wingless-type inducible signaling pathway protein-1 (WISP1), progranulin (PGRN), nesfatin-1 (nesfatin), visfatin/PBEF/NAMPT, apelin, retinol binding protein 4 (RPB4), and plasminogen activator inhibitor-1 (PAI-1) in the regulation of insulin resistance and vascular function, as well as many aspects of inflammation and immunity and their potential role in managing obesity-associated diseases, including metabolic, osteoarticular, and cardiovascular diseases.

Association of serum levels of secreted frizzled-related protein 5 and Wnt member 5a with glomerular filtration rate in patients with type 2 diabetes mellitus and chronic renal disease: a cross-sectional study

BACKGROUND

Diabetic nephropathy is a common complication of chronic kidney disease (CKD). -Inflammation in the kidneys is crucial for promoting development and progression of this complication. Wnt member 5a (Wnt5a) and secreted frizzled-related protein 5 (Sfrp5) are proinflammatory proteins associated with insulin resistance and chronic low-grade adipose tissue inflammation.

OBJECTIVE

To determine the correlation between serum Sfrp5 and Wnt5a concentrations and glomerular filtration rate in patients with type 2 diabetes mellitus and CKD.

DESIGN AND SETTING

Cross-sectional, comparative and observational study in the Department of Endocrinology, Civil Hospital, Culiacán, Sinaloa, Mexico.

METHODS

Eighty individuals with chronic kidney disease were recruited. Their serum Sfrp5 and Wnt5a concentrations were quantified using the enzyme-linked immunosorbent assay (ELISA) test. The statistical analysis consisted of the Mann-Whitney U test for independent samples and Spearman correlation, with statistical significance of P < 0.05.

RESULTS

Serum Sfrp5 concentration continually increased through the stages of CKD progression, whereas serum Wnt5a concentration presented its highest levels in stage 3 CKD. Negative correlations between estimated glomerular filtration rate (eGFR) and serum concentrations of Sfrp5 (r = -0434, P = 0.001) and Wnt5a (r = -0481, P = 0.001) were found.

CONCLUSIONS

There were negative correlations between serum Sfrp5 and Wnt5a concentrations and eGFR at each stage of CKD, with higher levels in female patients. This phenomenon suggests that Sfrp5 and Wnt5a might be involved in development and evolution towards end-stage renal disease.

Central Sfrp5 regulates hepatic glucose flux and VLDL-triglyceride secretion

OBJECTIVE

Secreted frizzled-related protein 5 (Sfrp5) has been shown to be associated with energy homeostasis and insulin resistance in mouse models of obesity and diabetes. However, its central role in glucose and lipid metabolism is unknown.

METHODS

HFD-fed rats received ICV infusions of vehicle or Sfrp5 during a pancreatic euglycemic clamp procedure. To delineate the pathway(s) by which ICV Sfrp5 modulates HGP and VLDL-TG secretion, we inhibited the hypothalamic K_ATP channel using glibenclamide, the DVC NMDA receptor with MK801, and selectively transected the hepatic branch of the vagal nerve while centrally infusing Sfrp5.

RESULTS

ICV Sfrp5 in HFD-fed rats significantly increased the glucose infusion required to maintain euglycemia due to HGP inhibition during the clamp procedure; moreover, hepatic PEPCK and G6Pase expression was decreased, and InsR and Akt phosphorylation was increased in the liver. ICV Sfrp5 also decreased circulating triglyceride levels via inhibiting hepatic VLDL-TG secretion. These changes were accompanied by the inhibition of enzymes related to lipogenesis in the liver. ICV Sfrp5 significantly increased insulin-stimulated phosphorylation of InsR and Akt in the hypothalamus of HFD-fed rats, and insulin-stimulated immunodetectable PIP3 levels were higher in Sfrp5 group than in control group both in vitro and vivo. The glucose- and lipid-lowering effects of ICV Sfrp5 were eliminated by NMDA receptor or DVC K_ATP channel inhibition or HVAG.

CONCLUSIONS

The present study demonstrates that central Sfrp5 signaling activates a previously unappreciated InsR-Akt-PI3k-K_ATP channel pathway in the hypothalamus and brain-hepatic vagus neurocircuitry to decrease HGP and VLDL-TG secretion.

Sfrp5/Wnt Pathway: A Protective Regulatory System in Atherosclerotic Cardiovascular Disease

Adipose tissue stores energy and is the largest endocrine organ in the body, producing several adipokines. However, among these adipokines, few play a role in the positive metabolism that promotes good health. Secreted frizzled-related protein (Sfrp)-5, an antagonist that directly binds to Wnt, has attracted interest due to its favorable effects on atherosclerotic cardiovascular disease (ASCVD). This review focuses on Sfrp5 biology and the roles of the Sfrp5/Wnt system in ASCVD.

Vitamin D3 supplementation improves serum SFRP5 and Wnt5a levels in patients with type 2 diabetes: A randomized, double-blind, placebo-controlled trial

Objective: To explore the effect of vitamin D3 on novel serum adipokines, secreted frizzled-related protein 5 (SFRP5) and Wingless-Type MMTV Integration Site Family Member 5a (Wnt5a) levels in Type 2 Diabetes Mellitus (T2DM) patients. Methods: Forty patients (16 women and 24 men) with type 2 diabetes participated in this double-blind, randomized, placebo-controlled clinical trial study. Participants were randomly assigned to receive 4000 IU vitamin D₃ (n = 20) or placebo (n = 20) daily for 2 months. Anthropometric indices, fasting blood glucose (FBS), hemoglobin A1c (HbA1c), insulin, serum tumor necrosis factor (TNF)-α, Wnt5a, SFRP5, physical activity, lipid profile, dietary intake, and serum calcidiol were assessed at the baseline and after 8 weeks. Results: In the group receiving Vitamin D, a significant increase in Calicidiol (15.03 ± 10.44 vs. 27.33 ± 11.2 ng/dl; P = < 0.001), SFRP5 (3.6 ± 0.46 vs. 3.98 ± 0.59 ng/ml; P = 0.01), and Wnt5a (0.33 ± 0.129 vs. 0.29 ± 0.047; P = 0.03) was observed. After two months supplementation, there were significant between-group differences in Calicidiol (27.33 ± 11.2 vs. 17.9 ± 12.95 ng/dl; P = 0.01), TNF-α (89.22 ± 34.28 vs. 164.93 ± 120.45 ng/ml; P = 0.006), Wnt5a (0.29 ± 0.047 vs. 0.33 ± 0.09; P = 0.04), and HbA1c (6.6 ± 0.96 % vs. 7.64 ± 1.15 %; p = 0.002). Moreover, the net changes (end - baseline) of Calicidiol (P = < 0.001), SFRP5 (P = 0.04), Wnt5a (P = 0.005), TNF-α (P = 0.01), insulin (P = 0.03), and QUICKI (P = 0.01) was significant between the groups. There were no significant effects on FBS and homeostasis model of assessment-estimated insulin resistance (HOMA-IR). Conclusion: 8 weeks of vitamin D3 supplementation for patients with type 2 diabetes may increase serum anti-inflammatory adipokine SFRP5 but decrease serum pro-inflammatory Wnt5a and TNF-α.

Sfrp5 increases glucose-stimulated insulin secretion in the rat pancreatic beta cell line INS-1E

Previous studies reported that secreted frizzled-related protein-5 (Sfrp5) decreases beta cell proliferation and increases fasting insulin levels, but studies on direct effects of Sfrp5 on insulin secretion and its underlying mechanisms are missing. This study examined effects of Sfrp5 on (i) beta cell viability and proliferation, (ii) basal and glucose-stimulated insulin secretion and (iii) canonical and non-canonical Wnt signalling pathways. We incubated rat INS-1E cells with 0.1, 1 or 5 μg/ml recombinant Sfrp5 for 24h. We measured basal and glucose-stimulated insulin secretion at glucose concentrations of 2.5 and 20 mmol/l. Phosphorylated and total protein content as well as mRNA levels of markers of cell proliferation, canonical and non-canonical Wnt signalling pathways were examined using Western blotting and real-time PCR. Differences between treatments were analysed by repeated measurement one-way ANOVA or Friedman’s test followed by correction for multiple testing using the Benjamini-Hochberg procedure. At 5 μg/ml, Sfrp5 reduced mRNA levels of cyclin-B1 by 25% (p<0.05). At 1 and 5 μg/ml, Sfrp5 increased glucose-stimulated insulin secretion by 24% and by 34% (both p<0.05), respectively, but had no impact on basal insulin secretion. Sfrp5 reduced the phosphorylation of the splicing forms p46 and p54 of JNK by 39% (p<0.01) and 49% (p<0.05), respectively. In conclusion, Sfrp5 reduced markers of cell proliferation, but increased in parallel dose-dependently glucose-stimulated insulin secretion in INS-1E cells. This effect is likely mediated by reduced JNK activity, an important component of the non-canonical Wnt signalling pathway.

Obesity and dyslipidemia

Obesity, a pandemic of the modern world, is intimately associated with dyslipidemia, which is mainly driven by the effects of insulin resistance and pro-inflammatory adipokines. However, recent evidence suggests that obesity-induced dyslipidemia is not a unique pathophysiological entity, but rather has distinct characteristics depending on many individual factors. In line with that, in a subgroup of metabolically healthy obese (MHO) individuals, dyslipidemia is less prominent or even absent. In this review, we will address the main characteristics of dyslipidemia and mechanisms that induce its development in obesity. The fields, which should be further investigated to expand our knowledge on obesity-related dyslipidemia and potentially yield new strategies for prevention and management of cardiometabolic risk, will be highlighted. Also, we will discuss recent findings on novel lipid biomarkers in obesity, in particular proprotein convertase subtilisin/kexin type 9 (PCSK9), as the key molecule that regulates metabolism of low-density lipoproteins (LDL), and sphingosine-1-phosphate (S1P), as one of the most important mediators of high-density lipoprotein (HDL) particles function. Special attention will be given to microRNAs and their potential use as biomarkers of obesity-associated dyslipidemia.

The effect of serum and follicular fluid secreted frizzle-related protein-5 on in vitro fertilization outcomes in patients with polycystic ovary syndrome

In this study, we aimed to investigate serum and follicular fluid (FF) secreted frizzle-related protein-5 (Sfrp-5) levels in nonobese, nonhyperandrogenic patients with polycystic ovary syndrome (PCOS) undergoing in vitro fertilization (IVF), in addition to IVF outcomes. In total, 160 patients undergoing IVF treatment were included in the study: 80 patients diagnosed with PCOS according to the Rotterdam criteria (group I, study) and 80 patients with the etiology of male factor infertility (group II, control). There were statistically significant between-group differences in serum estradiol (E₂) levels on the day of hCG administration (2377.00 ± 733.23 vs. 1931.3 ± 1,010.69), the total gonadotropin dose required (2000.63 ± 1,051.87 vs. 1.134.69 ± 286.45), and the total number of retrieved oocytes (8.60 ± 2.06 vs. 11.05 ± 4.39) (p < 0.05). There was also a statistically significant between-group difference in serum and FF Sfrp-5 levels on the day of oocyte retrieval (11.40 ± 2.88 vs. 8.87 ± 1.85, p < 0.001; 11.06 ± 2.30 vs. 9.71 ± 2.15, p = 0.008; respectively). However, there were no between-group differences in fertilization rates, clinical pregnancy rates, and live birth rates (p > 0.05). A correlation analysis showed that serum and FF Sfrp-5 levels were associated with insulin and inflammatory markers (p < 0.05). In a selected population of nonobese, nonhyperandrogenic PCOS patients, there was a significant difference in Sfrp-5 levels of the PCOS group versus those of the control group. Further studies are needed to determine the effects of Sfrp-5 in women with PCOS.

SFRP5 serves a beneficial role in arterial aging by inhibiting the proliferation, migration and inflammation of smooth muscle cells

Secreted frizzled-related protein 5 (SFRP5) is one of the anti-inflammatory adipokines secreted from white adipose tissue. However, little is known about the effect of SFRP5 on the cardiovascular system. The aim of the present study was to determine the effect of SFRP5 on smooth muscle cell (SMC) proliferation, migration and inflammation. The plasma levels of SFRP5 were evaluated in a cohort‑based elderly population using ELISA, and the expression of SFRP5 in Sprague‑Dawley rat aortas was detected using immunohistochemistry. SMC proliferation and migration were evaluated in vitro using 5‑ethynyl‑2'‑deoxyuridine cell proliferation and wound‑healing assays, respectively, while reactive oxygen species (ROS) production and cell signaling were assessed using a 2',7'‑dichlorodihydrofluorescein diacetate assay and immunoblotting, respectively. The results revealed that plasma levels of SFRP5 were positively correlated with age in the elderly Chinese cohort. Similarly, aorta SFRP5 expression was significantly higher in 15‑month‑old rats compared with 6‑month‑old rats. In vitro, SFRP5 significantly inhibited rat aortic SMC proliferation and migration that were induced by platelet‑derived growth factor (PDGF)‑BB, as well as inhibiting ROS generation. Compared with the effect of PDGF‑BB on SMCs, SFRP5 at 100 and 200 ng/ml significantly decreased SMC proliferation by 31.5 and 34.8%, respectively (P<0.05). SFRP5 at 100 and 200 ng/ml also inhibited the migration of SMCs by 24.9 and 28.4%, respectively, when compared with the effects of PDGF‑BB. SFRP5 attenuated the PDGF‑BB‑induced expression of β‑catenin and proliferating cell nuclear antigen, while p38 phosphorylation was significantly attenuated. Together, the present results suggested that SFRP5 may inhibit SMC proliferation, migration and inflammation by suppressing the Wnt/β‑catenin and p38/mitogen‑activated protein kinase signaling pathways.

Type 2 diabetes - An autoinflammatory disease driven by metabolic stress

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

Insulin resistance is associated with Sfrp5 in obstructive sleep apnea

Introduction

Obstructive sleep apnea, a common disease, is usually complicated by insulin resistance and type 2 diabetes mellitus. Adipokine is considered to play an important role in the development of insulin resistance and type 2 diabetes mellitus in obstructive sleep apnea.

Objective

To assess whether secreted frizzled-related protein 5, a new adipokine, is involved in untreated obstructive sleep apnea patients.

Methods

Seventy-six subjects with obstructive sleep apnea and thirty-three control subjects without obstructive sleep apnea were recruited and matched in terms of body mass index and age. The fasting secreted frizzled-related protein 5 plasma concentration was tested using ELISA. In addition, the correlation between secreted frizzled-related protein 5 and the homeostasis model assessment of insulin resistance was obtained. Multiple linear regression analysis models with stepwise selection were performed to determine the independent associations between various factors and secreted frizzled-related protein 5.

Results

Plasma secreted frizzled-related protein 5 levels were significantly lower in the obstructive sleep apnea group than in the control group (obstructive sleep apnea group: 28.44 ± 13.25 ng/L; control group: 34.16 ± 13.51 ng/L; p = 0.023). In addition, secreted frizzled-related protein 5 was negatively correlated with homeostasis model assessment of insulin resistance but positively correlated with the mean and lowest oxygen saturation with or without adjusting for age, gender, body mass index, neck circumference, waist circumference and waist-to-hip ratio. The multiple linear regression analysis showed there was an independent negative association between secreted frizzled-related protein 5 and homeostasis model assessment of insulin resistance.

Conclusion

Secreted frizzled-related protein 5 was involved in obstructive sleep apnea and the decrease in secreted frizzled-related protein 5 was directly proportional to the severity of obstructive sleep apnea. There was an independent negative correlation between homeostasis model assessment of insulin resistance and secreted frizzled-related protein 5 in the obstructive sleep apnea group. Secreted frizzled-related protein 5 might be a therapeutic target for insulin resistance in obstructive sleep apnea.

Circulating secreted frizzled-related protein 5 and chronic kidney disease in patients with acute ST-segment elevation myocardial infarction

Secreted frizzled-related protein-5 (Sfrp5) known as secreted antagonist binds to Wnt protein. It has been shown to be downregulated by histone acetylation and promoter methylation, and to function as a tumor suppressor gene by inducing apoptosis in renal cell cancer cells. However, its relationship with chronic kidney disease (CKD) has not been well studied. Our objective was to investigate the effect of plasma Sfrp5 levels in subjects with and without CKD. Plasma Sfrp5 levels were determined by enzyme-linked immunosorbent assays in 196 consecutive patients with acute ST-segment elevation myocardial infarction (STEMI). CKD was defined as an estimated glomerular filtration rate (eGFR) <60 ml/min per 1.73 m². For the purpose of this study, stage 1 or 2 CKD patients (eGFR ≥ 60 ml/min per 1.73 m²) were classified as not having CKD. With increasing Sfrp5 tertiles, the patients had higher frequencies of hypertension, stage 4 or 5 CKD, and waist-to-hip ratio, incrementally lower eGFRs and serum hemoglobin levels, and higher levels of blood urine nitrogen (BUN), creatinine, and adiponectin. Multivariate logistic regression analysis showed that an increased plasma Sfrp5 level was independently associated with CKD for all subjects (adjusted odds ratio (OR), 1.08; 95% confidence interval (CI), 1.02-1.14; p = 0.011). Sfrp5 was also significantly positively related to BUN, creatinine, and adiponectin, and significantly negatively related to eGFR and hemoglobin. When the patients were stratified by age, plasma Sfrp5 level was independently related to CKD for patients >65 years old (adjusted OR, 1.10; 95% CI, 1.00-1.20; p = 0.045), however, the association was not significant for those <65 years old. In addition, Sfrp5 was significantly positively related to BUN, creatinine, and adiponectin, and significantly negatively related to eGFR and hemoglobin in patients >65 years old. Our results suggest that Sfrp5 may play a role in the pathogenesis of CKD in acute STEMI patients who are older than 65 years.

Effect of SFRP5 (Secreted Frizzled-Related Protein 5) on the WNT5A (Wingless-Type Family Member 5A)-Induced Endothelial Dysfunction and Its Relevance With Arterial Stiffness in Human Subjects

OBJECTIVE

SFRP5 (secreted frizzled-related protein 5) is an endogenous inhibitor of WNT5A (wingless-type family member 5a), which has been implicated in atherosclerosis. However, contradictory results have been reported about the role of SFRP5 in atherosclerosis. We aimed to investigate whether SFRP5 could restore WNT5A-induced endothelial dysfunction in vitro and ex vivo. In addition, we sought to determine whether the serum concentration of SFRP5 is associated with atherosclerosis in humans.

APPROACH AND RESULTS

We measured endothelium-dependent vasorelaxation in the isolated thoracic aorta of Sprague-Dawley rats. In addition, we measured intracellular nitric oxide (NO) in human endothelial cells. The protein abundance of total and phosphorylated JNK (c-Jun N-terminal kinase), AKT (protein kinase B), and endothelial NO synthase was analyzed in human endothelial cells. Circulating SFRP5 and WNT5A levels and brachial-ankle pulse wave velocity were measured in 282 human subjects with type 2 diabetes mellitus. SFRP5 dose dependently restored Wnt5-induced impaired vasorelaxation in rat thoracic aorta by an endothelial NO synthase-dependent mechanism. SFRP5 treatment restored the WNT5A-induced reduction of NO production via endothelial NO synthase in human endothelial cells. WNT5A-induced changes in the phosphorylation of JNK, AKT, and endothelial NO synthase were ameliorated with SFRP5 administration. In humans with type 2 diabetes mellitus, the serum SFRP5 concentration positively correlated with brachial-ankle pulse wave velocity (r=0.146; P=0.024). Multivariate linear regression analysis demonstrated that the serum SFRP5 concentration was independently associated with brachial-ankle pulse wave velocity after adjustment for potential confounders [B (SE)=7.40 (3.35); P=0.028].

CONCLUSIONS

Our data suggest the possible compensatory action of SFRP5 against atherosclerosis under conditions of metabolic dysfunction.

Association of asymptomatic target organ damage with secreted frizzled related protein 5 in the elderly: the Northern Shanghai Study

Objective

Secreted frizzled related protein 5 (SFRP5) is a novel anti-inflammatory adipokine that is implicated in metabolic and cardiovascular disease (CVD). However, little is known about the relevance of SFRP5 with asymptomatic hypertensive target organ damages (TODs). We aimed to investigate the association between SFRP5 and TOD in a large population.

Clinical trial registration

NCT02368938.

Methods

A total of 1,745 community-dwelling elderly subjects aged over 65 years from northern Shanghai were recruited in the study. Plasma SFRP5 level was measured by an enzyme-linked immunosorbent assay. Asymptomatic TODs, including left ventricular mass index, peak transmitral pulsed Doppler velocity/early diastolic tissue Doppler velocity, carotid intima–media thickness (CIMT), pulse wave velocity (PWV), estimated glomerular filtration rate, and urinary albumin–creatinine ratio were evaluated.

Results

Plasma SFRP5 level was negatively associated with body mass index, waist/hip ratio, and fasting blood glucose (all P<0.001). Men, compared with women, had lower plasma SFRP5 level (4.19 vs 5.13 ng/mL, P<0.001). Additionally, plasma SFRP5 level was lower in diabetics than in those without diabetes (4.30 vs 4.81 ng/mL, P<0.05). Furthermore, an inverse association was observed between SFRP5 and PWV and CIMT (both P<0.05). Lastly, the multivariate logistic regression analysis showed lower SFRP5 level was significantly associated with increased arterial stiffness in the elderly (odds ratio 0.83, 95% confidence interval 0.71 to 0.99 per 1 standard deviation increase, P<0.05).

Conclusion

Plasma SFRP5 level was inversely correlated with conventional cardiovascular risk factors, and low plasma SFRP5 was also significantly associated with arterial stiffening in the elderly Chinese population.

SFRP5 is a target gene transcriptionally regulated by PPARγ in 3T3-L1 adipocytes

Secreted frizzled-related protein 5 (SFRP5) is a newly identified adipokine. SFRP5 expression increases during the differentiation and maturation of adipocytes, but the factors regulating SFRP5 expression during this process remain unclear. This study showed that peroxisome proliferator-activated receptor γ (PPARγ) adenovirus transfection could enhance the SFRP5 expression of 3T3-L1 adipocytes. Three potential binding sites of PPARγ in the SFRP5 promoter domain were found by bioinformatics analysis. Luciferase reporter gene assay demonstrated that PPARγ regulated the activity of the SFRP5 promoter through cis-acting elements at -2,284--1,500bp. Further experiments verified that PPARγ could specifically bind to the SFRP5 promoter at -2,284--2,263bp using chromatin immunoprecipitation and electrophoretic mobility shift assay. These results suggest that SFRP5 be a target gene of PPARγ, and its expression may be under the transcriptional regulation of PPARγ.

Inverse associations between serum levels of secreted frizzled-related protein-5 (SFRP5) and multiple cardiometabolic risk factors: KORA F4 study

Aims

Secreted frizzled-related protein (Sfrp)5 has beneficial effects on insulin sensitivity, inflammation and cardiovascular risk in different mouse models, but its relevance for cardiometabolic diseases in humans is controversial. We aimed to characterise associations of circulating SFRP5 with cardiometabolic risk factors and prediabetes/type 2 diabetes in a large population-based cohort.

Methods

Cross-sectional associations between serum SFRP5 and cardiometabolic risk factors as well as prediabetes/type 2 diabetes were investigated in 1096 participants aged 62–81 years from the German KORA F4 study, of whom 666 had prediabetes or type 2 diabetes. Multivariable linear regression models were adjusted for potential confounders including age, sex, body mass index (BMI), lifestyle factors, lipids, hypertension, kidney function and myocardial infarction.

Results

Higher serum SFRP5 levels were associated with lower HbA1c, BMI, systolic blood pressure, estimated glomerular filtration rate and high-sensitivity C-reactive protein levels and with higher levels of high-density lipoprotein cholesterol and adiponectin in the fully adjusted model (all P < 0.009). In contrast, favourable associations between SFRP5 and glycaemia, insulin, insulin resistance and other cardiometabolic risk factors were attenuated after adjustment for BMI. Serum SFRP5 levels were lower in participants with prediabetes or type 2 diabetes [(median (25th; 75th percentile) 48.8 (35.5; 65.7) ng/ml] compared to participants with normal glucose tolerance [55.9 (42.6; 69.6) ng/ml] (P < 0.001). In the fully adjusted model, higher SFRP5 was associated with lower odds of prediabetes/type 2 diabetes [OR (95% CI) (0.72 (0.58; 0.89)) per doubling of SFRP5, P < 0.01].

Conclusions

Higher serum SFRP5 was inversely associated with multiple risk factors for type 2 diabetes and cardiovascular diseases. However, BMI represents a strong confounder of some of these associations. Higher circulating SFRP5 was also associated with lower odds of prediabetes/type 2 diabetes, and this association was independent of BMI. Thus, SFRP5 emerges as novel biomarker that merits further research in the context of prevention of cardiometabolic diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-017-0591-x) contains supplementary material, which is available to authorized users.

Obesity-Induced Changes in Adipose Tissue Microenvironment and Their Impact on Cardiovascular Disease

Obesity is causally linked with the development of cardiovascular disorders. Accumulating evidence indicates that cardiovascular disease is the collateral damage of obesity-driven adipose tissue dysfunction that promotes a chronic inflammatory state within the organism. Adipose tissues secrete bioactive substances, referred to as adipokines, which largely function as modulators of inflammation. The microenvironment of adipose tissue will affect the adipokine secretome, having actions on remote tissues. Obesity typically leads to the upregulation of proinflammatory adipokines and the downregulation of anti-inflammatory adipokines, thereby contributing to the pathogenesis of cardiovascular diseases. In this review, we focus on the microenvironment of adipose tissue and how it influences cardiovascular disorders, including atherosclerosis and ischemic heart diseases, through the systemic actions of adipokines.

Bone marrow sFRP5 level is negatively associated with bone formation markers

Secreted frizzled-related protein 5 (sFRP5) level in bone marrow environment is inversely correlated with bone formation markers, suggesting that it decreases bone mass by inhibiting bone formation. Besides, it functions in a local fashion when regulating bone metabolism. sFRP5 may be a target when developing anti-osteoporotic agents.

INTRODUCTION

The purpose of the study is to investigate the relationship between bone marrow sFRP5 level and bone turnover state.

METHODS

Eighty-three total knee arthroplasty patients were enrolled in this study. Data were collected prospectively and reviewed retrospectively. Lumbar spine and femoral neck bone mineral density (BMD), marrow adipose tissue (MAT) sFRP5 messenger RNA (mRNA) expression level, sFRP5 concentrations in marrow fluid and serum, concentrations of bone formation and resorption markers were measured for each participant.

RESULTS

Marrow fluid sFRP5 concentration was positively correlated with both MAT sFRP5 expression (p = 0.040) and serum sFRP5 concentration (p = 0.043). Significantly positive correlation existed between MAT sFRP5 expression level and BMD (p < 0.05). Marrow fluid sFRP5 concentration had a moderate but not significant positive association with BMD. MAT sFRP5 was negatively related to serum bone formation markers including N-terminal propeptide of type 1 procollagen (P1NP) (p = 0.011), osteocalcin (OC), and alkaline phosphatase (ALP). Marrow fluid and serum sFRP5 concentrations also had mild negative correlations with bone formation markers but reached no significance. There was no significant correlation between bone resorption marker β-crosslaps (β-CTX) and sFRP5. The mRNA expression level of MAT sFRP5 was positively related with those of MAT leptin, peroxisome proliferator-activated receptor-γ (PPARγ), and adiponectin, and its correlation with leptin was statistically significant (p = 0.026).

CONCLUSIONS

Bone marrow sFRP5 level is closely correlated with BMD and bone formation markers. sFRP5 may be a potential negative regulator of bone mass by inhibiting bone formation. It may exert its effects on bone metabolism in a paracrine, rather than endocrine manner.

Sfrp5 associates with beta-cell function in humans

BACKGROUND

Secreted frizzled-related protein (Sfrp)5 improves insulin sensitivity, but impairs beta-cell function in rodents. However, the relationship between Sfrp5, insulin sensitivity and secretion in humans is currently unclear. Therefore, the aim of the study was to characterize the associations between serum Sfrp5 and indices of insulin sensitivity and beta-cell function from dynamic measurements using oral glucose tolerance tests (OGTT) in humans.

MATERIAL AND METHODS

This study enrolled 194 individuals with nonalcoholic fatty liver disease (NAFLD), who were diagnosed based on ultrasound and liver transaminases and underwent a frequent sampling 75-g OGTT. Fasting serum Sfrp5 was measured by ELISA. Associations were assessed with several indices of insulin sensitivity and beta-cell function derived from glucose, insulin and C-peptide concentrations during the OGTT.

RESULTS

Circulating Sfrp5 associated inversely with the insulinogenic index based on C-peptide (rs = -0·244, P = 0·001), but not with the insulinogenic index based on insulin levels (rs = -0·007, P = 0·926) after adjustment for age, sex and body mass index. Sfrp5 inversely correlated only with QUICKI as a marker of insulin sensitivity in the model adjusted for age and sex (rs = -0·149, P = 0·039). These associations were not influenced by the additional adjustment for hepatic steatosis index.

CONCLUSIONS

The inverse association of serum Sfrp5 with beta-cell function suggests a detrimental role of Sfrp5 for insulin secretion also in humans. The severity of NAFLD does not appear to affect this relationship. The weak association between serum Sfrp5 and insulin sensitivity was partially explained by body mass.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

Angiotensin II increases secreted frizzled-related protein 5 (sFRP5) expression through AT1 receptor/Rho/ROCK1/JNK signaling in cardiomyocytes

Secreted frizzled-related protein 5 (sFRP5) is a novel adipokine that functions as an inhibitor of Wnt signaling and is involved in embryonic development, proliferation, atherosclerosis, and apoptosis. Studies have shown that sFRP1-4 is expressed in cardiomyocytes, and sFRP3 and sFRP4 are elevated during heart failure. However, it is unclear whether sFRP5 is expressed in cardiomyocytes or cardiac hypertrophy, and as regards the effects of sFRP5 in the process. Here, we report the expression and the corresponding mechanisms of sFRP5 in angiotensin II (Ang II)-induced cardiomyocyte hypertrophy. Neonatal rat ventricular myocytes were exposed to increasing concentrations of Ang II for 12-72 h. Y27632 was used to block ROCK signal. PD98059, SB203580, and SP600125 were used to inhibit ERK1/2, p38 MAPK, and JNK signaling pathways, respectively, and anisomycin was used to activate JNK pathway. RT-PCR and Western-blot determined the expressions of sFRP5. BNP, TNF-α, ROCK1, ROCK2, MYPT1, and JNK were examined through Western-blot analysis. Ang II increased sFRP5 mRNA and protein levels in a time- and dose-dependent manner. Telmisartan, Y27632 and SP600125 effectively suppressed the expression of sFRP5. sFRP5 downregulated BNP and TNF-α expressions in hypertrophic cardiomyocytes. sFRP5 is expressed in cardiomyocytes, and upregulated in Ang II-induced cardiomyocyte hypertrophy through the AT1 receptor/Rho/ROCK1/JNK signaling pathway. sFRP5 may play an important role during cardiomyocyte hypertrophy.

Prediction of gestational diabetes mellitus by first trimester serum secreted frizzle-related protein-5 levels

OBJECTIVE

The main aim of this study was to investigate the first trimester maternal serum secreted frizzle-related protein-5 (Sfrp-5) levels and to evaluate the predictive value on the subsequently developed gestational diabetes mellitus (GDM).

METHODS

A total of 40 pregnant women who subsequently developed GDM and 44 age- and pre-pregnancy BMI-matched healthy pregnant women were enrolled in this prospective case-control study. First trimester serum Sfrp-5 levels were evaluated to determine if there is an association with the onset of GDM, by using logistic regression analysis.

RESULTS

Decreased first trimester serum Sfrp-5 levels (OR = 14.332, 95%CI: 4.166-49.301, p < 0.001) were found to be significantly associated with the increased risk of GDM. There were no statistically significant differences in serum Sfrp-5 levels between the diet- and insulin-treated GDM groups and also serum Sfrp-5 levels were not found to be predictive for adverse perinatal outcomes (p > 0.05).

CONCLUSIONS

Decreased first trimester serum Sfrp-5 levels are significantly associated with the increased risk of GDM.

Circulating SFRP5 levels are elevated in drug-naïve recently diagnosed type 2 diabetic patients as compared with prediabetic subjects and controls

BACKGROUND

Secreted frizzled-related protein 5 (SFRP5) has been linked to obesity. Results are conflicting regarding its association with type 2 diabetes (T2D) in humans. We aimed to investigate circulating SFRP5 in prediabetes and T2D and its potential association with parameters of insulin resistance and beta-cell function.

METHODS

We studied 70 drug-naïve T2D patients, 70 prediabetic subjects and 70 controls. All subjects were body mass index matched to the T2D patients and overweight or obese. SFRP5, hormones and cytokines levels were measured by ELISA.

RESULTS

Serum SFRP5 levels were elevated in T2D patients as compared with prediabetic subjects (median 15.6, interquartile range [9-24.5] ng/mL vs 9.8 [5-14.2] ng/mL, p < 0.001, respectively) and controls (15.6 [9-24.5] ng/mL vs 10.4 [6.7-16.6] ng/mL, P < 0.001, respectively). No differences were found in serum SFRP5 levels between prediabetic subjects and controls (9.8 [5-14.2] ng/mL vs 10.4 [6.7-16.6] ng/mL, p = 0.472, respectively). After adjusting for potential confounders (age, gender, body mass index, triglycerides, high-density lipoprotein cholesterol and blood pressure), T2D was still associated with higher values of SFRP5 as compared with prediabetes in multinomial logistic regression analysis (fully adjusted odds ratio 3.50, 95% confidence interval 1.40-8.79, p = 0.008). The association was more subtle when comparing T2D with normal glucose tolerance state (fully adjusted odds ratio 2.18, 95% confidence interval 0.91-5.21, p = 0.078).

CONCLUSIONS

Circulating SFRP5 levels were independently associated with T2D as compared with prediabetes and normal glucose tolerance state.

Inhibition of secreted frizzled-related protein 5 improves glucose metabolism

Elucidating the role of secreted frizzled-related protein 5 (SFRP5) in metabolism and obesity has been complicated by contradictory findings when knockout mice were used to determine metabolic phenotypes. By overexpressing SFRP5 in obese, prediabetic mice we consistently observed elevated hyperglycemia and glucose intolerance, supporting SFRP5 as a negative regulator of glucose metabolism. Accordingly, Sfrp5 mRNA expression analysis of both epididymal and subcutaneous adipose depots of mice indicated a correlation with obesity. Thus, we generated a monoclonal antibody (mAb) against SFRP5 to ascertain the effect of SFRP5 inhibition in vivo. Congruent with SFRP5 overexpression worsening blood glucose levels and glucose intolerance, anti-SFRP5 mAb therapy improved these phenotypes in vivo. The results from both the overexpression and mAb inhibition studies suggest a role for SFRP5 in glucose metabolism and pancreatic β-cell function and thus establish the use of an anti-SFRP5 mAb as a potential approach to treat type 2 diabetes.

SFRP5 acts as a mature adipocyte marker but not as a regulator in adipogenesis

WNT/β-catenin signalling is involved in regulating adipogenesis, and its dysregulation occurs in obesity. Secreted frizzled-related protein 5 (SFRP5) is a WNT protein inhibitor; however, its role in adipogenesis and obesity is controversial. In this study, we observed that SFRP5 mRNA levels were increased in the fat tissues of obese humans and mice. Sfrp5 expression was gradually induced during differentiation of white and brown adipocytes and was highly increased in mature adipocytes rather than preadipocytes. However, the effects of the exogenous overexpression of Sfrp5 indicated that Sfrp5 may not directly regulate adipogenesis in vitro under the conditions studied. Moreover, SFRP5 did not inhibit the canonical WNT/β-catenin signalling pathway in preadipocytes. Subsequently, we measured the levels of circulating SFRP5 in obese patients and non-obese subjects using ELISA and did not find any significant difference. Collectively, these findings indicate that Sfrp5 represents a candidate for a mature adipocyte marker gene. Our data provide new evidence concerning the role of SFRP5 in adipogenesis of white and brown adipocytes and obesity.

Association of secreted frizzled-related protein 4 (SFRP4) with type 2 diabetes in patients with stable coronary artery disease

Background

Secreted frizzled-related proteins (SFRP) are regulators of Wnt-signalling. SFRP4 has been shown to regulate insulin exocytosis and is overexpressed in type 2 diabetes mellitus.

Here we characterized the relation of SFRP4 to glucose and triglyceride metabolism and outcomes in patients with stable coronary artery disease on statin treatment in the prospective Homburg Cream & Sugar Study (NCT00628524).

Methods

Fasting SFRP4 concentrations were measured by ELISA in 504 consecutive patients with stable CAD confirmed by angiography.

Results

The median age was 68 years and 83% of patients were male. Oral glucose tolerance tests were performed in all patients without known diabetes for metabolic characterization. 24.4% of patients showed normal glucose tolerance, 29.4% impaired glucose tolerance and 46.2% diabetes mellitus. SFRP4 concentrations correlated with insulin (R = 0.153, p = 0.001), HbA1c (R = 0.166, p < 0.0001), fasting triglycerides (R = 0.113, p = 0.011) and higher triglycerides after lipid challenge (postprandial triglycerides R = 0.124, p = 0.005; AUC R = 0.134, p = 0.003). Higher SFRP4 concentrations were associated with type 2 diabetes, metabolic syndrome, and severity of diabetes.

The primary outcome was the composite of cardiovascular death and cardiovascular hospitalization within 48 months follow-up. Comparison of event-free survival between SFRP4 tertiles showed that SFRP4 concentrations were not predictive for cardiovascular outcome.

Conclusions

SFRP4 concentrations are associated with impaired glucose and triglyceride metabolism but do not predict cardiovascular outcome in patients with stable coronary artery disease on treatment.

SFRP5 correlates with obesity and metabolic syndrome and increases after weight loss in children

OBJECTIVE

Secreted frizzled-related protein 5 (SFRP5) is a novel anti-inflammatory adipokine, which has been shown as a mediator between obesity and its comorbidities. The aim of this study was to evaluate the associations of SFRP5 with metabolic syndrome (MetS) and the effects of lifestyle interventions on circulating SFRP5 levels in children.

DESIGN

A cross-sectional study was conducted among 111 obese children and 49 lean controls, and a lifestyle intervention was performed in a subgroup of 31 obese children for 6 months. Anthropometric parameters, clinical data and circulating SFRP5 levels were measured at baseline and after lifestyle intervention.

RESULTS

Secreted frizzled-related protein 5 was significantly lower in obese children, especially in those with MetS, and negatively correlated with body mass index (BMI), waist circumference and homeostasis model assessment of insulin resistance. Independent of other well-known risk factors, SFRP5 was a significant predictor of MetS in children. In the longitudinal study, lifestyle intervention led to significant weight loss and higher SFRP5 levels. Furthermore, changes in BMI significantly correlated with the rising magnitude of SFRP5.

CONCLUSIONS

Serum SFRP5 is regulated by weight status and seems to be correlated with metabolic disorders in children.

Activation of noncanonical Wnt signaling through WNT5A in visceral adipose tissue of obese subjects is related to inflammation

CONTEXT

Wingless-type mouse mammary tumor virus integration site family (WNT)-5A is a glycoprotein involved in the regulation of the inflammatory response by activating the noncanonical Wnt signaling pathway. Secreted frizzled-related protein (SFRP)-5 acts as a decoy receptor that binds and sequesters WNT5A, preventing activation of frizzled receptors and attenuating the noncanonical Wnt signaling.

OBJECTIVE

The aim of the study was to evaluate the involvement of WNT5A and SFRP5 in obesity and obesity-related comorbidities as well as to explore their effect in visceral adipose tissue inflammation.

PATIENTS AND METHODS

Samples obtained from 90 subjects were used. Circulating and gene expression levels of WNT5A and SFRP5 were analyzed in different metabolic tissues. The effect of TNF-α and lipopolysaccharide on the transcript levels of WNT5A and SFRP5 in adipocytes was explored. We also investigated whether WNT5A itself can activate an inflammatory response.

RESULTS

Increased circulating levels of WNT5A in obese patients (P < .05) were decreased (P < .001) after gastric bypass. In this line, WNT5A mRNA in visceral adipose tissue was increased (P < .05) in obese patients with gene expression levels of SFRP5 being down-regulated (P < .05). WNT5A mRNA expression was significantly enhanced (P < .01) by lipopolysaccharide and TNF-α treatment, whereas no effects were found in SFRP5 gene expression levels. Furthermore, exogenous WNT5A induced (P < .05) IL-6, IL1B, MMP2, MMP9, and SSP1 mRNA expression in human adipocyte cultures.

CONCLUSIONS

Activation of noncanonical Wnt signaling through the up-regulation of WNT5A and down-regulation of SFRP5 may promote a proinflammatory state in visceral adipose tissue contributing to the development of obesity-associated comorbidities.

Is Alzheimer's disease related to metabolic syndrome? A Wnt signaling conundrum

Alzheimer's disease (AD) is the most common cause of dementia, affecting more than 36 million people worldwide. AD is characterized by a progressive loss of cognitive functions. For years, it has been thought that age is the main risk factor for AD. Recent studies suggest that life style factors, including nutritional behaviors, play a critical role in the onset of dementia. Evidence about the relationship between nutritional behavior and AD includes the role of conditions such as obesity, hypertension, dyslipidemia and elevated glucose levels. The coexistence of some of these cardio-metabolic risk factors is generally known as metabolic syndrome (MS). Some clinical studies support the role of MS in the onset of AD. However, the cross-talk between the molecular signaling implicated in these disorders is unknown. In the present review, we focus on the molecular correlates that support the relationship between MS and the onset of AD. We also discuss relevant issues such as the role of leptin, insulin and renin-angiotensin signaling in the brain and the possible role of Wnt signaling in both MS and AD. We discuss the evidence supporting the use of ob/ob mice, high-fructose diets, aortic coarctation-induced hypertension and Octodon degus, which spontaneously develops β-amyloid deposits and metabolic derangements, as suitable animal models to address the relationships between MS and AD. Finally, we examine emergent data supporting the role of Wnt signaling in the modulation of AD and MS, implicating this pathway as a therapeutic target in both conditions.

Balanced duo of anti-inflammatory SFRP5 and proinflammatory WNT5A in children

BACKGROUND

Secreted frizzled-related protein 5 (SFRP5) is an adipokine protecting against obesity-related insulin resistance and diabetes. SFRP5 binds to wingless type mouse mammary tumor virus (MMTV) integration site family member 5A (WNT5A) to improve insulin sensitivity. We performed the first study of SFRP5 and WNT5A simultaneously in children.

METHODS

Prepubertal children (n = 342) were assessed for circulating SFRP5 (all subjects) and circulating WNT5A (210 subjects), and associations were sought with metabolic markers. In conditioned media of adipose tissue explants from 12 additional children, SFRP5 and WNT5A were studied further.

RESULTS

The concentrations of SFRP5 and WNT5A correlated positively in serum and in conditioned media (all P < 0.001). Lower level of circulating SFRP5 (lowest quartile) was associated with higher BMI (15% increase, P < 0.0001) and lower level of high-molecular-weight adiponectin (26% decrease, P = 0.002). Circulating WNT5A related closely with insulin resistance assessed by the homeostasis model assessment for insulin resistance and hepatic markers (alanine transaminase and gamma glutamyl transpeptidase), particularly in children with lower circulating SFRP5 levels (all P < 0.004).

CONCLUSION

SFRP5 and WNT5A comprise a balanced duo that may regulate metabolic homeostasis in prepubertal children.

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

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

Adipocytokines in obesity and metabolic disease

The current global obesity pandemic is the leading cause for the soaring rates of metabolic diseases, especially diabetes, cardiovascular disease, hypertension, and non-alcoholic hepatosteatosis. Efforts devoted to find cures for obesity and associated disorders in the past two decades have prompted intensive interest in adipocyte biology, and have led to major advances in the mechanistic understanding of adipose tissue as an essential endocrine organ. Adipose tissue secretes an array of hormones (adipokines) that signal key organs to maintain metabolic homeostasis, and their dysfunction has been causally linked to a wide range of metabolic diseases. In addition, obesity induces production of inflammatory cytokines (often referred to together with adipokines as adipocytokines) and infiltration of immune cells into adipose tissue, which creates a state of chronic low-grade inflammation. Metabolic inflammation has been increasingly recognized as a unifying mechanism linking obesity to a broad spectrum of pathological conditions. This review focuses on classic examples of adipocytokines that have helped to form the basis of the endocrine and inflammatory roles of adipose tissue, and it also details a few newly characterized adipocytokines that provide fresh insights into adipose biology. Studies of adipocytokines in clinical settings and their therapeutic potential are also discussed.

Low serum level of secreted frizzled-related protein 5, an anti-inflammatory adipokine, is associated with coronary artery disease

OBJECTIVE

Secreted frizzled-related protein 5 (SFRP5) is an anti-inflammatory adipokine that is associated with insulin resistance in animals. To extend these observations to humans, we investigated the association of serum SFRP5 levels in subjects with and without coronary artery disease (CAD).

METHODS

Subjects (n=185, 68±11 years, 79% male) suspected of having CAD were enrolled in the study and were divided into two groups, CAD and non-CAD subjects, according to the results of their coronary angiographies. Serum SFRP5 levels of the subjects were measured by an enzyme-linked immunosorbent assay.

RESULTS

The serum SFRP5 levels in the subjects with CAD were significantly lower than those in the non-CAD subjects (median [interquartile range]: 47.7 [26.6] vs. 52.4 [29.6] ng/mL, respectively; p=0.02). The serum SFRP5 levels significantly correlated with body mass index, the homeostasis model of assessment of insulin resistance, adiponectin levels, and CAD severity. Multivariate logistic regression analysis revealed that a decreased serum SFRP5 level (log transformed) was independently associated with CAD for all subjects (adjusted odds ratio, 0.36; 95% confidence interval, 0.14-0.94; p=0.03).

CONCLUSION

Serum SFRP5 levels are significantly associated with CAD in humans, suggesting that low SFRP5 levels may contribute to CAD.

Anti-inflammatory cytokines and risk of type 2 diabetes

Proinflammatory processes have been investigated extensively in the development of type 2 diabetes, but our knowledge on anti-inflammatory proteins is rather limited. This article summarizes studies that investigated associations between circulating levels of anti-inflammatory cytokines and incident type 2 diabetes preferably in prospective epidemiological studies. Adiponectin is the only known anti-inflammatory protein whose circulating levels are decreased before type 2 diabetes. In contrast, concentrations of interleukin-1 receptor antagonist (IL-1RA), transforming growth factor-β1 (TGF-β1) and growth differentiation factor-15 (GDF-15) are increased and indicate the presence of a compensatory, but eventually futile, counter-regulation of proinflammatory stimuli. Importantly, a proof-of-principle study using recombinant IL-1RA to improve metabolic control in patients with type 2 diabetes demonstrated that a more pronounced upregulation of this protein than that found in the natural course of diabetes development may have clinical relevance. Other interesting candidates like omentin (which shows similar associations with metabolic parameters as adiponectin), interleukin-10 (IL-10) and secreted frizzled-related protein-5 (Sfrp5) are currently less well studied with sometimes conflicting results regarding their association with type 2 diabetes. Thus, further research is required to better understand the causal role of proinflammatory cytokines, hypoadiponectinaemia and the upregulation of anti-inflammatory proteins before the onset of type 2 diabetes.

The Emerging Health Benefits of Coffee with an Emphasis on Type 2 Diabetes and Cardiovascular Disease

Debate persists whether coffee is beneficial or problematic for human health. Coffee consumption has been associated with a decrease in risk of developing type 2 diabetes, and numerous epidemiological studies have demonstrated that healthy, habitual coffee drinkers are more protected from the risk of contracting diabetes than individuals who do not drink coffee. Coffee consumption has been associated with a reduced incidence of impaired glucose tolerance, hyperglycaemia and insulin sensitivity. Data suggest that several coffee components, such as chlorogenic acids, are involved in the health benefits of coffee. Various mechanisms for this protective effect have been proposed, including effects on incretin release, liver glucose metabolism and insulin sensitivity. Epidemiological data support numerous other health benefits for coffee, including reduced cardiovascular disease (CVD), a protective effect against some neurodegenerative conditions, a favourable effect on liver function and a protective effect against certain cancers These associations are based mainly on observational studies and are currently insufficient to recommend coffee consumption as an interventional strategy for risk reduction in type 2 diabetes and other metabolic diseases While excessive consumption can have adverse effects on some conditions, particularly in terms of sleep quality, these effects vary among individuals and most people do not have any symptoms from coffee drinking. Moderate coffee consumption is associated with no or little risk of severe diseases and may offer substantial health benefits. Thus, coffee is a safe, low-energy beverage and suitable for most adult people.

Fibroblasts derive from hepatocytes in liver fibrosis via epithelial to mesenchymal transition

Secreted frizzled-related protein 5 (Sfrp5) is an adipokine with anti-inflammatory and insulin-sensitizing properties in mice. However, the mechanism of Sfrp5 action, especially in humans, is largely unknown. Therefore, cytokine release and insulin signaling were analyzed to investigate the impact of Sfrp5 on inflammation and insulin signaling in primary human adipocytes and skeletal muscle cells (hSkMC). Sfrp5 neither affected interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1) and adiponectin release from human adipocytes, nor IL-6 and IL-8 release from hSkMC. In tumor necrosis factor (TNF) α-treated adipocytes, Sfrp5 reduced IL-6 release by 49% (p<0.05), but did not affect MCP-1 and adiponectin release. In MCP-1-treated hSkMC, Sfrp5 did not affect cytokine secretion. In untreated adipocytes, Sfrp5 decreased the insulin-mediated phosphorylation of Akt-Ser473, Akt-Thr308, GSK3α-Ser21 and PRAS40-Thr246 by 34% (p<0.01), 31% (p<0.05), 37% (p<0.05) and 34% (p<0.01), respectively, and the stimulation of glucose uptake by 25% (p<0.05). Incubation with TNFα increased the phosphorylation of JNK and NFκB, and impaired insulin signaling. When Sfrp5 and TNFα were combined, there was no additional effect on insulin signaling and JNK phosphorylation, but phosphorylation of NFκB was reversed to basal levels. Sfrp5 had no effect on insulin signaling in untreated or in MCP-1 treated hSkMC. Thus, Sfrp5 lowered IL-6 release and NFκB phosphorylation in cytokine-treated human adipocytes, but not under normal conditions, and decreased insulin signaling in untreated human adipocytes. Sfrp5 did not act on hSkMC. Therefore, the cellular actions of Sfrp5 seem to depend on the type of tissue as well as its inflammatory and metabolic state.