Serum fetuin-A concentrations are elevated in subjects with impaired glucose tolerance and newly diagnosed type 2 diabetes

Fetuin-A: a relevant novel serum biomarker for non-invasive diagnosis of metabolic dysfunction-associated steatotic liver disease (MASLD): a retrospective case-control study

OBJECTIVES

To determine how fetuin-A contributes to diagnosing and assessing MASLD severity.

METHODS

Fifty MASLD patients and fifty healthy control participants were involved in this retrospective case-control research. Abdominal ultrasonography, fibroscan with controlled attenuated parameter scan (CAP scan), laboratory investigation (including fetuin-A assessment), clinical examination, and history-taking were performed on every case.

RESULTS

Fetuin-A level was considerably higher in the Cases group (1154.85 ± 629.89) than in the Control group (505.29 ± 150.4) (p < 0.001). Fetuin-A had significant validity in the prediction of MASLD at a cut-off > 702.5 with 82% sensitivity, 90% specificity, and 86% overall accuracy.

CONCLUSION

One possible marker for MASLD diagnosis could be fetuin-A. Furthermore, a substantial association between such marker and the severity of the disease as it revealed a significant correlation with ultrasound grading and fibroscan with controlled attenuated parameters. Trial registration 1- Pan African Clinical Trial Registry. Unique Identifying number/registration ID: PACTR202309644280965. URL: https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=26860 . Registration Approval date: 21/09/2023. 2- ClinicalTrials.gov. Unique Identifying number /registration ID: NCT06097039. URL: https://clinicaltrials.gov/study/NCT06097039?cond=NCT06097039&rank=1 . Registration Approval date: 25/10/2023.

A secondary analysis of indices of hepatic and beta cell function following 12 weeks of carbohydrate and energy restriction vs. free-living control in adults with type 2 diabetes

BACKGROUND

Substantial weight loss in people living with type 2 diabetes (T2D) can reduce the need for glucose-lowering medications while concurrently lowering glycemia below the diagnostic threshold for the disease. Furthermore, weight-loss interventions have also been demonstrated to improve aspects of underlying T2D pathophysiology related to ectopic fat in the liver and pancreatic beta-cell function. As such, the purpose of this secondary analysis was to explore the extent to which a low-carbohydrate and energy-restricted (LCER) diet intervention improves markers of beta-cell stress/function, liver fat accumulation, and metabolic related liver function in people with type 2 diabetes.

METHODS

We conducted secondary analyses of blood samples from a larger pragmatic community-based parallel-group randomized controlled trial involving a 12-week pharmacist implemented LCER diet (Pharm-TCR: <50 g carbohydrates; ~850-1100 kcal/day; n = 20) versus treatment-as-usual (TAU; n = 16). Participants were people with T2D, using ≥ 1 glucose-lowering medication, and a body mass index of ≥ 30 kg/m2. Main outcomes were C-peptide to proinsulin ratio, circulating microRNA 375 (miR375), homeostatic model assessment (HOMA) beta-cell function (B), fatty liver index (FLI), hepatic steatosis index (HSI), HOMA insulin resistance (IR), and circulating fetuin-A and fibroblast growth factor 21 (FGF21). Data were analysed using linear regression with baseline as a covariate.

RESULTS

There was no observed change in miR375 (p = 0.42), C-peptide to proinsulin ratio (p = 0.17) or HOMA B (p = 0.15). FLI and HSI were reduced by -25.1 (p < 0.0001) and - 4.9 (p < 0.0001), respectively. HOMA IR was reduced by -46.5% (p = 0.011). FGF21 was reduced by -161.2pg/mL (p = 0.035) with a similar tendency found for fetuin-A (mean difference: -16.7ng/mL; p = 0.11). These improvements in markers of hepatic function were accompanied by reductions in circulating metabolites linked to hepatic insulin resistance (e.g., diacylglycerols, ceramides) in the Pharm TCR group.

CONCLUSIONS

The Pharm-TCR intervention did not improve fasting indices of beta-cell stress; however, markers of liver fat accumulation and and liver function were improved, suggesting that a LCER diet can improve some aspects of the underlying pathophysiology of T2D.

TRIAL REGISTRATION

Clinicaltrials.gov (NCT03181165).

Investigation of Fetuin-A pathway in diabetes mellitus formation in rats exposed to elf magnetic fields

The presence of technological devices in our lives has increased exposure to environmental electromagnetic fields. As a result of this, especially Cancer and Diabetes are increasing.Rats were divided into 3 groups with 12 rats in each group. The 1st experimental group (n = 12) was exposed to a 50 Hz ELF magnetic field of 0.4 mT for 6 hours a day for 5 days, the 2nd experimental group (n = 12) was exposed for 10 days, and the control group (n = 12) was never exposed to a magnetic field. After completing the applications, blood collection from the rats was performed under appropriate conditions, measurements were made in the laboratory, and statistical analysis was performed between the groups. There was no significant difference between the groups in the results of transaminases and lipid profiles and C-Peptide. There was no significant difference in insulin, urea, creatinine, Na, K, Ca, and uric acid parameters between the groups. However, there was a significant increase in glucose, HbA1c, and Hba1 IFCC values between the control group and the experimental groups (p < .001). There was a significant increase in the level of Fetuin-A between the control group and the experimental groups (p < .05). There was an increase in the Fetuin-A, Glucose, HbA1c, and Hba1c IFCC values in both of the experimental groups compared to the control group. We believe that an increase in these values may cause Type 3 diabetes.

AMP activated kinase negatively regulates hepatic Fetuin-A via p38 MAPK-C/EBPβ/E3 Ubiquitin Ligase Signaling pathway

Fetuin-A (Fet-A) is a liver-secreted phosphorylated protein, known to impair insulin signaling, which has been shown to be associated with obesity, insulin resistance, and incident diabetes. Fet-A interacts with the insulin-stimulated insulin receptor (IR) and inhibits IR tyrosine kinase activity and glucose uptake. It has been shown that high glucose increases Fet-A expression through the ERK1/2 signaling pathway. However, factors that downregulate Fet-A expression and their potential mechanisms are unclear. We examined the effect of AMP-activated protein kinase (AMPK) on high-glucose induced Fet-A expression in HepG2 cells, Hep3B cells and primary rat hepatocytes. High glucose increased Fet-A and phosphorylated (Ser312) fetuin-A (pFet-A) expression, which are known to impair insulin signaling. AICAR-induced AMPK activation significantly down-regulated high glucose-induced Fet-A expression and secretion of pFet-A while treatment with Compound C (AMPK inhibitor), SB202190 (p38 MAPK inhibitor) or p38 MAPK siRNA transfection prevented AICAR-induced downregulation of Fet-A expression. In addition, activation of p38 MAPK, by anisomycin, decreased the hepatic expression of Fet-A. Further, we our studies have shown that short-term effect of AICAR-treatment on Fet-A expression was mediated by proteosomal degradation, and long-term treatment of AICAR was associated with decrease in hepatic expression of C/EBP beta, an important transcription factor involved in the regulation of Fet-A. Taken together, our studies implicate a critical role for AMPK-p38 MAPK-C/EBPb-ubiquitin-proteosomal axis in the regulation of the expression of hepatic Fet-A.

Novel Biomolecules in the Pathogenesis of Gestational Diabetes Mellitus 2.0

Gestational diabetes mellitus (GDM) has become a major public health problem and one of the most discussed issues in modern obstetrics. GDM is associated with serious adverse perinatal outcomes and long-term health consequences for both the mother and child. Currently, the importance and purposefulness of finding a biopredictor that will enable the identification of women with an increased risk of developing GDM as early as the beginning of pregnancy are highly emphasized. Both “older” molecules, such as adiponectin and leptin, and “newer” adipokines, including fatty acid-binding protein 4 (FABP4), have proven to be of pathophysiological importance in GDM. Therefore, in our previous review, we presented 13 novel biomolecules, i.e., galectins, growth differentiation factor-15, chemerin, omentin-1, osteocalcin, resistin, visfatin, vaspin, irisin, apelin, FABP4, fibroblast growth factor 21, and lipocalin-2. The purpose of this review is to present the potential and importance of another nine lesser known molecules in the pathogenesis of GDM, i.e., 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), angiopoietin-like protein-8 (ANGPTL-8), nesfatin-1, afamin, adropin, fetuin-A, zonulin, secreted frizzled-related proteins (SFRPs), and amylin. It seems that two of them, fetuin-A and zonulin in high serum levels, may be applied as biopredictors of GDM.

Proteomic Analysis of Aqueous Humor Proteins in Association with Cataract Risks: Diabetes and Smoking

Cataracts are one of the most common eye diseases that can cause blindness. Discovering susceptibility factors in the proteome that contribute to cataract development would be helpful in gaining new insights in the molecular mechanisms of the cataract process. We used label-free nanoflow ultra-high-performance liquid chromatography–tandem mass spectrometry to compare aqueous humor protein expressions in cataract patients with different cataract risk factors such as diabetes mellitus (DM) and smoking and in controls (with cataract) without risk exposure. Eight patients with diabetes and who smoked (with double risk factors), five patients with diabetes and five patients who smoked (both with a single risk factor), and nine aged-matched cataract controls patients (non-risk exposure) were enrolled. In total, 136 aqueous humor proteins were identified, of which only alpha-2-Heremans–Schmid (HS)-glycoprotein was considered to be significantly risk-associated because it was differentially expressed in these three groups and exhibited increased expression with increasing risk factors. Significant changes in the aqueous humor level of alpha-2-HS-glycoprotein between DM and control samples and between smoking and control samples were confirmed using ELISA. The alpha-2-HS-glycoprotein, called fetuin-a, could be a potential aqueous biomarker associated with DM and smoking, which were cataract risk factors.

Fetuin-A in newly detected type 2 diabetes mellitus as a marker of non-alcoholic fatty liver disease

INTRODUCTION

Fetuin-A has been implicated in the causation of metabolic disorders such as obesity, diabetes, and hepatic steatosis. Numerous studies have shown the association between levels of fetuin-A in type 2 diabetes mellitus (T2DM) and non-alcoholic fatty liver disease (NAFLD). The levels of fetuin-A in newly detected type 2 diabetic (NDD) patients and its relationship with the presence of NAFLD have not been studied.

OBJECTIVE

To study the fetuin-A levels in patients with NDD and its relationship with NAFLD.

METHODS

A total of 60 NDD patients were studied. The diagnosis of NAFLD was made on the basis of transient elastography. Serum fetuin-A and serum fasting insulin were measured along with other investigations.

RESULTS

The percentage of patients with NAFLD in NDD was 53.33%. Fetuin-A levels were significantly higher in NDD with NAFLD compared to those without NAFLD. There was no association of fetuin-A with age, systolic and diastolic blood pressure, fasting blood sugar (FBS), hemoglobin (Hb)A1c, fasting insulin, homeostatic model assessment-insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), and markers of advanced fibrosis. Fetuin-A levels beyond 1166.5 mcg/mL could predict the development of NAFLD with odds ratio (OR) of 4.33 (95% CI: 1.364-13.77), which remained significant after adjustment for various confounding factors.

CONCLUSION

Fetuin-A is a reliable marker of NAFLD in NDD and is positively associated with insulin resistance (IR). The observation in this study suggests that high serum fetuin-A levels in patients with NAFLD do not merely reflect the effects of insulin resistance, but also a more extensive distortion of liver architecture.

Fetuin-A as a Marker of Insulin Resistance

Fetuin–A is a glycoprotein which helps in the regulation of metabolism. It is an early marker of insulin resistance (IR). The aim of this study was to evaluate the role of Fetuin–A as a predictive biomarker in cases of newly detected type 2 diabetes (NDD). The study involved 60 NDD and 60 Normal Healthy Controls (NHC). All the demographics and anthropological characteristics were noted. Fasting blood samples were drawn and various biochemical parameters were analyzed. The homeostatic model assessment of insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI) score was calculated. Chisquare, student T-test and Mann Whitney U tests were employed to associate and compare the mean and median between the NDD and NHC groups. Pearson's and Spearman’s correlation analysis were employed to examine the relationship of Fetuin–A levels with parametric and nonparametric variables. The independent predictors of Fetuin–A was determined by employing multiple forward linear regression. Fetuin–A was significantly high in NDD compared to NHC (1323 vs. 306.98 mcg/mL; p<0.001). Majority of NDD patients demonstrated IR based on the HOMA-IR (88.33% vs. 66.67%) and QUICKI score (96.67% vs. 85%). The multiple linear regression analysis showed that systolic blood pressure, age and QUICKI score were independently associated with Fetuin–A (p value <0.01). Fetuin–A may be used as a biomarker to detect NDD. Therefore, early detection of Fetuin–A levels in NDD gives an opportunity for suitable patient management.

Investigation of proteins important for microcirculation using in vivo microdialysis after glucose provocation: a proteomic study

Insulin has metabolic and vascular effects in the human body. What mechanisms that orchestrate the effects in the microcirculation, and how the responds differ in different tissues, is however not fully understood. It is therefore of interest to search for markers in microdialysate that may be related to the microcirculation. This study aims to identify proteins related to microvascular changes in different tissue compartments after glucose provocation using in vivo microdialysis. Microdialysis was conducted in three different tissue compartments (intracutaneous, subcutaneous and intravenous) from healthy subjects. Microdialysate was collected during three time periods; recovery after catheter insertion, baseline and glucose provocation, and analyzed using proteomics. Altogether, 126 proteins were detected. Multivariate data analysis showed that the differences in protein expression levels during the three time periods, including comparison before and after glucose provocation, were most pronounced in the intracutaneous and subcutaneous compartments. Four proteins with vascular effects were identified (angiotensinogen, kininogen-1, alpha-2-HS-glycoprotein and hemoglobin subunit beta), all upregulated after glucose provocation compared to baseline in all three compartments. Glucose provocation is known to cause insulin-induced vasodilation through the nitric oxide pathway, and this study indicates that this is facilitated through the interactions of the RAS (angiotensinogen) and kallikrein-kinin (kininogen-1) systems.

The Evolving Role of Fetuin-A in Nonalcoholic Fatty Liver Disease: An Overview from Liver to the Heart

Nonalcoholic fatty liver disease (NAFLD) is strongly associated to the features of metabolic syndrome which can progress to cirrhosis, liver failure and hepatocellular carcinoma. However, the most common cause of mortality in people with NAFLD is not liver-related but stems from atherosclerotic cardiovascular disease (CVD). The prevalence of NAFLD is on the rise, mainly as a consequence of its close association with two major worldwide epidemics, obesity and type 2 diabetes (T2D). The exact pathogenesis of NAFLD and especially the mechanisms leading to disease progression and CVD have not been completely elucidated. Human fetuin-A (alpha-2-Heremans Schmid glycoprotein), a glycoprotein produced by the liver and abundantly secreted into the circulation appears to play a role in insulin resistance, metabolic syndrome and inflammation. This review discusses the links between NAFLD and CVD by specifically focusing on fetuin-A’s function in the pathogenesis of NAFLD and atherosclerotic CVD.

Emerging Protein Biomarkers for the Diagnosis or Prediction of Gestational Diabetes-A Scoping Review

Introduction: Gestational diabetes (GDM), defined as hyperglycemia with onset or initial recognition during pregnancy, has a rising prevalence paralleling the rise in type 2 diabetes (T2DM) and obesity. GDM is associated with short-term and long-term consequences for both mother and child. Therefore, it is crucial we efficiently identify all cases and initiate early treatment, reducing fetal exposure to hyperglycemia and reducing GDM-related adverse pregnancy outcomes. For this reason, GDM screening is recommended as part of routine pregnancy care. The current screening method, the oral glucose tolerance test (OGTT), is a lengthy, cumbersome and inconvenient test with poor reproducibility. Newer biomarkers that do not necessitate a fasting sample are needed for the prompt diagnosis of GDM. The aim of this scoping review is to highlight and describe emerging protein biomarkers that fulfill these requirements for the diagnosis of GDM. Materials and Methods: This scoping review was conducted according to preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines for scoping reviews using Cochrane Central Register of Controlled Trials (CENTRAL), the Cumulative Index to Nursing & Allied Health Literature (CINAHL), PubMed, Embase and Web of Science with a double screening and extraction process. The search included all articles published in the literature to July 2020. Results: Of the 3519 original database citations identified, 385 were eligible for full-text review. Of these, 332 (86.2%) were included in the scoping review providing a total of 589 biomarkers studied in relation to GDM diagnosis. Given the high number of biomarkers identified, three post hoc criteria were introduced to reduce the items set for discussion: we chose only protein biomarkers with at least five citations in the articles identified by our search and published in the years 2017-2020. When applied, these criteria identified a total of 15 biomarkers, which went forward for review and discussion. Conclusions: This review details protein biomarkers that have been studied to find a suitable test for GDM diagnosis with the potential to replace the OGTT used in current GDM screening protocols. Ongoing research efforts will continue to identify more accurate and practical biomarkers to take GDM screening and diagnosis into the 21st century.

Hepatokines as a Molecular Transducer of Exercise

Exercise has health benefits and prevents a range of chronic diseases caused by physiological and biological changes in the whole body. Generally, the metabolic regulation of skeletal muscle through exercise is known to have a protective effect on the pathogenesis of metabolic syndrome, non-alcoholic fatty liver disease (NAFLD), type 2 diabetes (T2D), and cardiovascular disease (CVD). Besides this, the importance of the liver as an endocrine organ is a hot research topic. Hepatocytes also secrete many hepatokines in response to nutritional conditions and/or physical activity. In particular, certain hepatokines play a major role in the regulation of whole-body metabolic homeostasis. In this review, we summarize the recent research findings on the exercise-mediated regulation of hepatokines, including fibroblast growth factor 21, fetuin-A, angiopoietin-like protein 4, and follistatin. These hepatokines serve as molecular transducers of the metabolic benefits of physical activity in chronic metabolic diseases, including NAFLD, T2D, and CVDs, in various tissues.

Circulating levels of fetuin-A are associated with moderate-severe hepatic steatosis in young adults

PURPOSE

The hepatokine fetuin-A might have a role as molecular link between non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM). The aim of this study was to evaluate the association between fetuin-A and the prevalence and severity of NAFLD in a population of young adults.

METHODS

Ninety-seven adults (age 35.7 ± 12.4 years, female 64.9%), enrolled in a previous study evaluating NAFLD prevalence in the presence or absence of family history of T2DM, were included. Serum levels of fetuin-A (ELISA BioVendor, Czech Republic) and the main biochemical parameters were assessed. Presence and severity of NAFLD were evaluated by ultrasonography (Toshiba, Japan). A linear regression was run to predict fetuin-A levels and a logistic regression was performed to predict moderate-severe steatosis.

RESULTS

Fetuin-A associated inversely with age (ß - 0.12, p = 0.03) and directly with body mass index (BMI) (ß 0.5, p = 0.048), waist circumference (WC) (ß 0.3, p = 0.027), triglycerides (TG) (ß 0.1, p = 0.001) and uric acid (ß 1.7, p = 0.018), after adjustment for age and sex. In a model including age, BMI, WC, TG and uric acid, age (ß - 0.2, p = 0.002) and TG (ß 0.04, p = 0.02) were independent predictors of fetuin-A. Prevalence of steatosis was 66%. The rates of mild and moderate-severe steatosis were 50.5% and 15.5%, respectively. In the logistic model, the independent predictors of moderate-severe steatosis were fetuin-A (OR 1.22, p = 0.036), age (OR 1.17, p = 0.01) and BMI (OR 2.75, p = 0.011).

CONCLUSION

In a sample of young adults, circulating levels of fetuin-A correlated with moderate-severe NAFLD, independent of confounders, and with some metabolic parameters. Fetuin-A might be a useful marker to predict NAFLD and metabolic disorders.

Effects of fetuin-A with diverse functions and multiple mechanisms on human health

Fetuin-A (Alfa 2-Heremans-Schmid) is a glycoprotein that is mainly synthesized by hepatocytes and then released into the bloodstream. While fetuin-A, a multifunctional protein, has inhibitory effects on health in the processes of calcification, mineralization, coronary artery calcification (CAC), and kidney stone formation by various mechanisms, it has such stimulatory effects as obesity, diabetes, and tumor progression processes. Fetuin-A produces these effects on the organism mainly by playing a role in the secretion levels of some inflammatory cytokines and exosomes, preventing unwanted calcification, inhibiting the autophosphorylation of tyrosine kinase, suppressing the release of adiponectin and peroxisome proliferator-activated receptor-γ (PPARγ), activating the toll-like receptor 4 (TLR-4), triggering the phosphatidylinositol 3 (PI3) kinase/Akt signaling pathway and cell proliferation, and mimicking the transforming growth factor-beta (TGF-β) receptor. In the present review, fetuin-A was examined in a wide perspective from the structure and release of fetuin-A to its effects on health.

Diabetes-induced early molecular and functional changes in aortic heart valves in a murine model of atherosclerosis

Diabetes contributes directly to the development of cardiovascular aortic valve disease. There is currently no drug therapy available for a dysfunctional valve and this urges the need for additional research to identify distinctive mechanisms of cardiovascular aortic valve disease evolution. The aim of this study was to evaluate changes of valvular aortic lesions induced in a hyperlipemic ApoE^-/- mouse model by early type 1 diabetes onset (at 4 and 7 days after streptozotocin induction). The haemodynamic valve parameters were evaluated by echography and blood samples and aortic valves were collected. Plasma parameters were measured, and inflammatory, remodelling and osteogenic markers were evaluated in the aortic valves. Next, correlations between all parameters were determined. The results showed early aortic valve dysfunction detected by echography after 1 week of diabetes; lesions were found in the aortic root. Moreover, increased expression of cell adhesion molecules, extracellular matrix remodelling and osteogenic markers were detected in hyperlipemic ApoE^-/- diabetic mice. Significant correlations were found between tissue valve biomarkers and plasmatic and haemodynamic parameters. Our study may help to understand the mechanisms of aortic valve disease in the diabetic milieu in order to discover and validate new biomarkers of cardiovascular aortic valve disease in diabetes and reveal new possible targets for nanobiotherapies.

Fetuin-A Inhibits Placental Cell Growth and Ciliogenesis in Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a type of unbalanced glucose tolerance that occurs during pregnancy, which affects approximately 10% of pregnancies worldwide. Fetuin-A is associated with insulin resistance, and the concentration of circulating fetuin-A increases in women with GDM, however, the role of fetuin-A in the placenta remains unclear. In this study, we enrolled placental samples from twenty pregnant women with GDM and twenty non-GDM pregnant women and found that the abundance of fetuin-A was upregulated in terms of mRNA and protein levels. Fetuin-A inhibited placental cell growth by inducing apoptosis and inhibiting S phase entry. Irregular alignment of mitotic chromosomes and aberrant mitotic spindle poles were observed. In addition, centrosome amplification was induced by fetuin-A treatment, and these amplified centrosomes nucleated microtubules with disorganized microtubule arrays in placental cells. Furthermore, fetuin-A inhibited autophagy, and thus blocked the growth of the primary cilium, a cellular antenna that regulates placenta development and differentiation. Thus, our study uncovered the novel function of fetuin-A in regulating placental cell growth and ciliogenesis.

Organokines in disease

Studies have linked obesity, metabolic syndrome, type 2 diabetes, cardiovascular disease (CVD), nonalcoholic fatty liver disease (NAFLD) and dementia. Their relationship to the incidence and progression of these disease states suggests an interconnected pathogenesis involving chronic low-grade inflammation and oxidative stress. Metabolic syndrome represents comorbidities of central obesity, insulin resistance, dyslipidemia, hypertension and hyperglycemia associated with increased risk of type 2 diabetes, NAFLD, atherosclerotic CVD and neurodegenerative disease. As the socioeconomic burden for these diseases has grown signficantly with an increasing elderly population, new and alternative pharmacologic solutions for these cardiometabolic diseases are required. Adipose tissue, skeletal muscle and liver are central endocrine organs that regulate inflammation, energy and metabolic homeostasis, and the neuroendocrine axis through synthesis and secretion of adipokines, myokines, and hepatokines, respectively. These organokines affect each other and communicate through various endocrine, paracrine and autocrine pathways. The ultimate goal of this review is to provide a comprehensive understanding of organ crosstalk. This will include the roles of novel organokines in normal physiologic regulation and their pathophysiological effect in obesity, metabolic syndrome, type 2 diabetes, CVD, NAFLD and neurodegenerative disorders.

Role of exercise-induced hepatokines in metabolic disorders

The health-promoting effects of physical activity to prevent and treat metabolic disorders are numerous. However, the underlying molecular mechanisms are not yet completely deciphered. In recent years, studies have referred to the liver as an endocrine organ, since it releases specific proteins called hepatokines. Some of these hepatokines are involved in whole body metabolic homeostasis and are theorized to participate in the development of metabolic disease. In this regard, the present review describes the role of Fibroblast Growth Factor 21, Fetuin-A, Angiopoietin-like protein 4, and Follistatin in metabolic disease and their production in response to acute exercise. Also, we discuss the potential role of hepatokines in mediating the beneficial effects of regular exercise and the future challenges to the discovery of new exercise-induced hepatokines.

Prediction of gestational diabetes mellitus in the first trimester: comparison of maternal fetuin-A, N-terminal proatrial natriuretic peptide, high-sensitivity C-reactive protein, and fasting glucose levels

OBJECTIVE

We investigated the utility of maternal fetuin-A, N-terminal proatrial natriuretic peptide (pro-ANP), high-sensitivity C-reactive protein (hs-CRP), and fasting glucose levels at 11-14 gestation weeks for predicting pregnancies complicated by gestational diabetes mellitus (GDM).

SUBJECTS AND METHODS

This prospective cohort study included 327 low-risk pregnant women who completed antenatal follow-up at a tertiary research hospital between January and April 2014. Maternal blood samples were collected between 11-14 gestational weeks in the first trimester of pregnancy and then stored at -80 °C until further analyses. During follow-up, 29 (8.8%) women developed GDM. The study population was compared 1:2 with age- and body mass index-matched pregnant women who did not develop GDM (n = 59). Fasting plasma glucose (FPG) levels and serum fetuin-A, pro-ANP, and hs-CRP levels were measured using automated immunoassay systems.

RESULTS

There was a significant negative correlation between fetuin-A and hs-CRP (CC = -0.21, p = 0.047) and a positive correlation between FPG and hs-CRP (CC = 0.251, p = 0.018). The areas under the receiver operating characteristic curve for diagnosing GDM were 0.337 (p = 0.013), 0.702 (p = 0.002), and 0.738 (p < 0.001) for fetuin-A, hs-CRP, and FPG, respectively. The optimal cut-off values were > 4.65, < 166, and > 88.5 mg/dL for maternal hs-CRP, fetuin-A, and FPG, respectively.

CONCLUSION

Reduced fetuin-A, elevated hs-CRP, and FPG levels in women in the first trimester can be used for the early detection of GDM. Further research is needed before accepting these biomarkers as valid screening tests for GDM.

Fetuin-A levels are increased in the adipose tissue of diabetic obese humans but not in circulation

Background

The hepatokine fetuin-A is linked to obesity and type 2 diabetes, but its presence and expression in adipose tissue remain unclear. In this study, we aimed to assess the circulating levels of fetuin-A and its expression in subcutaneous adipose tissue (SAT) from diabetic and non-diabetic obese subjects and their modulation by exercise.

Methods

SAT and blood were obtained from adults obese (diabetic, n=118 and non-diabetic, n=166) before and after a 3-month exercise program (diabetic, n=40 and non-diabetic, n=36, respectively). Plasma fetuin-A was assayed using ELISA. The presence and expression of fetuin-A in SAT, peripheral blood mononuclear cells (PBMCs) and cell lines (3T3-L1, THP-1, HepG2, RAW 264.7) were analysed using confocal microscopy, immunoblotting and qRT-PCR.

Results

Plasma fetuin-A level did not significantly differ between diabetic and non-diabetic obese subjects. However, when the non-diabetic group was divided into metabolically healthy and unhealthy phenotypes, significantly higher fetuin-A level was observed in the unhealthy sub-group. Circulating fetuin-A was mainly associated with glycaemic markers. In SAT, fetuin-A protein level was significantly higher in the diabetic obese subjects but its mRNA was not detected. Similarly, fetuin-A protein was detected in PBMCs, but its mRNA was not. In line with this, the use of various cell lines and culture media indicated that the presence of fetuin-A in SAT and PBMCs was due to its uptake from circulation rather than its endogenous expression. Finally, physical exercise decreased fetuin-A levels in both plasma and SAT in both groups.

Conclusions

Fetuin-A levels increased in association with diabetes in SAT but not in circulation in the obese subjects. Moreover, physical exercise decreased fetuin-A level. Fetuin-A potentially acts as a hepatokine taken up by other tissues, such as adipose tissue.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0919-x) contains supplementary material, which is available to authorized users.

The association between fetuin-A and testosterone levels and markers of arterial stiffness in Saudi subjects with type 2 diabetes mellitus

BACKGROUND

Inconsistent results have been described regarding the part of fetuin-A and testosterone in arterial stiffness in type 2 diabetes mellitus (T2DM).

AIM

To look into the links of serum fetuin-A and testosterone levels with brachial-Ankle pulse wave velocity (baPWV), a marker of arteriosclerosis and common carotid intima media thickness (ccIMT), a marker of early atherosclerosis, in diabetic Saudi men patients.

SUBJECTS AND METHODS

One hundred and fifty adult male patients with T2DM and 60 non-diabetic control subjects were enrolled from different Saudi Arabia Taif hospitals. Biochemical analysis, anthropometric measurements, blood pressure, baPWV and ccIMT were investigated.

RESULTS

Stepwise regression in diabetic patients revealed that the most important predictor of ba-PWV was serum fetuin-A followed by serum glucose and the most important predictor of ccIMT was serum fetuin-A followed by serum HDL then serum triglycerides.

CONCLUSIONS

Only fetuin-A levels not testosterone are negatively associated with early markers of atherosclerosis.

Relationship of Serum Fetuin A with Metabolic and Clinical Parameters in German Children and Adolescents with Type 1 Diabetes

BACKGROUND AND AIM

The hepatokine fetuin A is upregulated in the metabolic syndrome and in type 2 diabetes (T2D), while its role in adolescent type 1 diabetes (T1D) is unclear. We assessed the relationship between circulating fetuin A levels and metabolic control, comorbidities, and complications in adolescent T1D patients.

METHODS

We studied the relationship between serum fetuin A and clinical diabetes-related data from the DPV registry (Diabetes-Pa-tienten-Verlaufsdokumentation) in 172 adolescent T1D patients with early-onset (<5 years) long-standing (>10 years) T1D. Fetuin A levels were further compared between adolescent T1D and T2D patients.

RESULTS

Serum fetuin A levels in T1D patients (mean 0.267 ± 0.043 g/L) did not correlate with age, diabetes duration, gender, body mass index (BMI), glycated hemoglobin, serum lipid levels, blood pressure, celiac or thyroid disease, nephropathy, or retinopathy. An association of fetuin A levels with insulin requirements was only evident within the subgroup of overweight T1D patients (rs = 0.439, p = 0.028, n = 25, BMI >90th percentile), disappearing after adjustment for multiple testing. Adolescent T1D patients showed distinctly lower fetuin A levels than patients with T2D (p ≤ 0.001).

CONCLUSION

Overall, we did not observe a clinically relevant association of fetuin A levels with surrogate parameters for insulin sensitivity in our juvenile T1D cohort. A correlation with insulin requirements was detectable in overweight patients only. We hypothesize that multiple factors, such as obesity, puberty, inadequate metabolic control, and hepatic steatosis, have to add up before a clinically relevant effect of fetuin A on insulin sensitivity becomes evident.

Associations of serum fetuin-A and oxidative stress parameters with polycystic ovary syndrome

Objective

The aim of this study was to compare serum fetuin-A levels and oxidative stress markers, as indicators of insulin resistance, in women with polycystic ovary syndrome (PCOS) and in healthy controls.

Methods

This prospective case-control study included 46 patients with PCOS and 48 age- and body mass index–matched control women. Levels of serum hormones, fetuin-A, and oxidative stress markers were measured in blood samples taken during the early follicular period from each participant.

Results

Follicle-stimulating hormone (FSH), luteinising hormone (LH), total testosterone levels, and the LH/FSH ratio were found to be significantly higher in women with PCOS than in controls. Serum total antioxidant status, total oxidant status, and oxidative stress index parameters all indicated significantly higher levels of oxidative stress in PCOS patients than in controls. Serum fetuin-A levels, which were analyzed as an indicator of insulin resistance, were higher in the PCOS group than in the control group (210.26±65.06 µg/mL and 182.68±51.20 µg/mL, respectively; p=0.024).

Conclusion

The data obtained from the present study suggest that higher levels of both serum fetuin-A and oxidative stress markers might be related with PCOS.

Melatonin improves insulin resistance and hepatic steatosis through attenuation of alpha-2-HS-glycoprotein

Melatonin plays an important role in regulating circadian rhythms. It also acts as a potent antioxidant and regulates glucose and lipid metabolism, although the exact action mechanism is not clear. The α2-HS-glycoprotein gene (AHSG) and its protein, fetuin-A (FETUA), are one of the hepatokines and are known to be associated with insulin resistance and type 2 diabetes. The aim of this study was to determine whether melatonin improves hepatic insulin resistance and hepatic steatosis in a FETUA-dependent manner. In HepG2 cells treated with 300 μmol/L of palmitic acid, phosphorylated AKT expression decreased, and FETUA expression increased, but this effect was inhibited by treatment with 10 μmol/L of melatonin. However, melatonin did not improve insulin resistance in FETUA-overexpressing cells, indicating that improvement in insulin resistance by melatonin was dependent on downregulation of FETUA. Moreover, melatonin decreased palmitic acid-induced ER stress markers, CHOP, Bip, ATF-6, XBP-1, ATF-4, and PERK. In addition, in the high-fat diet (HFD) mice, oral treatment with 100 mg/kg/day melatonin for 10 weeks reduced body weight gain to one-third of that of the HFD group and hepatic steatosis. Insulin sensitivity and glucose intolerance improved with the upregulation of muscle p-AKT protein expression. FETUA expression and ER stress markers in the liver and serum of HFD mice were decreased by melatonin treatment. In conclusion, melatonin can improve hepatic insulin resistance and hepatic steatosis through reduction in ER stress and the resultant AHSG expression.

Changes in Liver Gene Expression and Plasma Concentration of Rbp4, Fetuin-A, and Fgf21 in Sprague-Dawley Rats Subjected to Different Dietary Interventions and Bariatric Surgery

Purpose

To study the effect of duodenal-jejunal omega switch (DJOS) in combination with different dietary patterns on the retinol-binding protein (RBP4), fetuin-A, and fibroblast growth factor 21 (FGF21) plasma levels and their hepatic gene expressions in rats.

Methods

A high-fat diet (HF) was given to 28 rats and 28 more were fed with a control diet (CD) for 2 months. After that, half of each group underwent either DJOS or SHAM surgery. For the next 2 months, half of the animals in each operation group were kept on the same diet as before and half of them had the diet changed. After 16 weeks of the experiment RBP4, fetuin-A, and FGF21 plasma levels as well as liver Rbp4, Ahsg, and Fgf21 gene expressions were measured.

Results

DJOS had a reductive impact on plasma levels of RBP4, fetuin-A, and FGF21 and Rbp4, Ahsg, and Fgf21 relative gene expression in the liver when compared to SHAM. The HF/HF group expressed significantly higher RBP4 and fetuin-A plasma levels in comparison to the control. The HF diet used before and/or after surgery led to upregulation of Rbp4, Ahsg, and Fgf21 relative gene expression. The lowest levels of analyzed parameters were observed in the CD/CD group.

Conclusions

The efficiency of DJOS surgery, measured by hepatokines' plasma levels and their gene expressions in the liver, depends on the type of diet applied before and after surgery. Manipulation of dietary patterns can lead to marked improvements in metabolic profile after DJOS surgery.

Does bariatric surgery influence plasma levels of fetuin-A and leukocyte cell-derived chemotaxin-2 in patients with type 2 diabetes mellitus?

Background

Fetuin-A and leukocyte cell-derived chemotaxin-2 (LECT-2) are liver-derived proteins. Fetuin-A is an independent risk factor for type 2 diabetes (T2D) and obese patients with T2D have higher plasma fetuin-A levels than those without T2D. LECT-2 has positive correlation with the severity of both obesity and insulin resistance. The changes in plasma fetuin-A are not consistent after bariatric surgery and no studies have investigated the changes in LECT-2 on the obese patients with T2D after bariatric surgery.

Methods

Overall, 18 patients undergoing gastric bypass (GB) and 16 patients undergoing sleeve gastrectomy (SG) were enrolled. The fasting plasma fetuin-A and LECT-2 levels were measured at baseline, one week, three months, and one year after surgery.

Results

Both the GB and SG groups significantly decreased the body mass index (BMI), waist-to-hip ratio, a body shape index; the triglyceride, fasting blood sugar (FBS), hemoglobin A1c, C-peptide levels; and homeostatic model assessment (HOMA-IR) one year after surgery. The SG group showed a decreasing trend in plasma fetuin-A levels one year after SG surgery. There are no significant changes in LECT-2 one year after either GB or SG. Fetuin-A had a near significant negative relationship with insulin (P = 0.056) and HOMA-IR (P = 0.050) in the SG group. Changes in fetuin-A had a significant positive relationship with changes in BMI (P = 0.031) and waist-to-hip ratio (P = 0.031) in the GB group and had a near significant positive correlation with FBS (P = 0.051) in the SG group.

Discussion

Neither GB nor SG modifies plasma levels of plasma fetuin-A or LECT-2 in T2D patients after surgery. The changes in plasma fetuin-A have a positive correlation with those of the BMI and waist-to-hip ratio 12 months after GB.

The association between circulating fetuin-A levels and type 2 diabetes mellitus risk: systematic review and meta-analysis of observational studies

BACKGROUND AND OBJECTIVE

Fetuin-A is a liver-derived circulating protein that is associated with insulin resistance and diabetes. The objective of this systematic review and meta-analysis of published observational studies was to investigate mean levels of fetuin-A in T2D patients and the relationship between blood fetuin-A levels and T2D risk.

MATERIALS AND METHODS

PubMed, Embase, Google Scholar, Web of Science, and The Cochrane Library were systematically searched for potential relevant studies up to 1 December 2016. Natural logarithm-transformed estimate risks, standard mean differences on the basis of Hedges's adjusted g, and 95% confidence intervals (CIs) were calculated for all eligible studies and were combined to measure the pooled data using random-effects model.

RESULTS

A total of 32 studies including 27 case-control and 5 cohort studies were included in the current study. Fetuin-A levels in T2D patients were significantly higher than control groups [Hedges' g = 1.73, 95% CI (1.25-2.22), P < 0.001], with significant heterogeneity across studies (P < 0.001, I ² = 98.46%). Findings from meta-analyses of cohort studies showed a statistically significant association between fetuin-A levels and T2D risk [rate ratio = 1.62, 95% CI (1.26-2.08), P < 0.001], with no significant heterogeneity (P = 0.10, I ² = 46.06%).

CONCLUSION

We found a significant relationship between the fetuin-A levels with T2D risk. Although fetuin-A may be as a potential screening and prediction biomarker or a therapeutic target in T2D patients, further studies are required in this regard.

Fetuin-A levels and risk of type 2 diabetes mellitus: a systematic review and meta-analysis

AIMS

Fetuin-A has been linked to insulin resistance and obesity. Its role in the pathogenesis of type 2 diabetes (T2DM) has also been discussed. We aimed to investigate the prospective association of fetuin-A and the risk of T2DM in a systematic review and meta-analysis.

METHODS

A systematic search of studies from the MEDLINE, EMBASE, Pubmed and Web of Science using fetuin-A, diabetes and various synonyms was conducted up to June 5, 2017. Relevant studies were extracted by two reviewers independently. The quality of studies was assessed using Newcastle-Ottawa scales. Overall estimates were pooled using fixed effect with inverse variance meta-analysis. Subgroup analyses by gender, study population, techniques of assessing fetuin-A, diabetes ascertainment methods, follow-up duration and measures of association were conducted.

RESULTS

Seven studies comprising a total of 11,497 individuals and 2176 cases of T2DM were included in the systematic review and meta-analysis. Overall, one SD increment of fetuin-A level was associated with a 23% greater risk of incident T2DM (RR: 1.23, 95% CI 1.16-1.31). No significant heterogeneity or publication bias was found. The association was relatively stable across different subgroups. However, the association seemed only evident in women, but not in men.

CONCLUSIONS

Higher circulating fetuin-A levels were associated with increased risk of T2DM. However, the causality deserved further analysis.

Association of plasma fetuin-a levels with peripheral arterial disease and lower extremity arterial calcification in subjects with type 2 diabetes mellitus

AIMS

Fetuin-A is a hepatic glycoprotein that is involved in insulin resistance and atherosclerosis. Herein we examined the association of plasma fetuin-A levels with peripheral arterial disease (PAD) in patients with type 2 diabetes mellitus (T2DM).

MATERIAL AND METHODS

A total of 71 patients with T2DM and 57 non-diabetic individuals were recruited. Diagnosis of PAD was based on the absence of triphasic waveform at pedal arteries, while ankle-brachial index (ABI) was calculated. Radiographs of both feet and ankles were taken for the assessment of lower extremity arterial calcification (LEAC). Plasma fetuin-A levels were measured using ELISA.

RESULTS

Patients with T2DM had higher fetuin-A levels than non-diabetic participants. Participants with diabetes and PAD had lower fetuin-A levels than non-PAD diabetic patients. In subjects with T2DM fetuin-A levels were associated with ABI. Multivariate analysis demonstrated that in patients with T2DM the odds of PAD increased with long diabetes duration, smoking, presence of arterial hypertension and dyslipidemia, as well as with lower fetuin-A levels. A trend towards higher fetuin-A levels in subjects with less severe LEAC was found.

CONCLUSION

Plasma fetuin-A levels are lower in patients with T2DM and PAD and are associated with PAD, irrespective of traditional cardiovascular risk factors. Moreover, fetuin-A may be involved in arterial calcification.

Emerging Human Fetuin A Assays for Biomedical Diagnostics

Human fetuin A (HFA) plays a prominent pathophysiological role in numerous diseases and pathophysiological conditions with considerable biomedical significance; one example is the formation of calciprotein particles in osteoporosis and impaired calcium metabolisms. With impressive advances in in vitro diagnostic assays during the last decade, ELISAs have become a workhorse in routine clinical diagnostics. Recent diagnostic formats involve high-sensitivity immunoassay procedures, surface plasmon resonance, rapid immunoassay chemistries, signal enhancement, and smartphone detection. The current trend is toward fully integrated lab-on-chip platforms with smartphone readouts, enabling health-care practitioners and even patients to monitor pathological changes in biomarker levels. This review provides a critical analysis of advances made in HFA assays along with the challenges and future prospects.

Cardiotrophin-1 is associated with increased risk of arterial stiffness

AIM

Cardiotrophin-1 null mice presented decreased arterial stiffness. The aim of this study is to investigate the relationship between cardiotrophin-1 and arterial stiffness, assessed by brachial-ankle pulse-wave velocity (baPWV).

METHODS

We enrolled 300 subjects, 200 with baPWV >1400 and 100 with baPWV ≤1400 cm/s.

RESULTS

Cardiotrophin-1 levels were significantly higher in subjects with baPWV >1400 than those with baPWV ≤1400 cm/s. The multivariate logistic regression analysis showed that age, prehypertension, hypertension and cardiotrophin-1 were independently associated with baPWV >1400 cm/s after adjusting for gender, obesity, diabetes, homeostasis model assessment-insulin resistance, total cholesterol, high-density lipoprotein cholesterol, triglyceride, high-sensitivity C-reactive protein, creatinine, smoking and habitual exercise.

CONCLUSION

Cardiotrophin-1 is positively related to baPWV independent of traditional cardiometabolic risk factors for arterial stiffness.

Relation of Serum and Vitreous Concentrations of Fetuin-A with Diabetic Retinopathy

Background

Fetuin-A, a liver-derived glycoprotein, is correlated with diabetes. The aim of the present investigation was to evaluate serum and vitreous concentrations of fetuin-A in patients with diabetic retinopathy (DR).

Material/Methods

We randomly selected 224 diabetic patients and 68 control subjects for this study.

Results

There were markedly higher serum and vitreous fetuin-A concentrations in proliferative diabetic retinopathy (PDR) patients than in the other three groups. NPDR patients exhibited elevated vitreous fetuin-A concentrations compared with patients without DR. However, no significant differences in serum fetuin-A concentrations were observed between NPDR patients and patients without DR. In addition, there were significantly lower concentrations of serum and vitreous fetuin-A in control subjects compared with the other three groups.

Conclusions

The occurrence and severity of DR is correlated with serum and vitreous fetuin-A concentrations.

Serum fetuin-A concentrations are positively associated with serum VEGF levels in patients with newly diagnosed type 2 diabetes

Fetuin-A was considered to be involved in pathogenesis of type 2 diabetes. On the other hand, higher vascular endothelial growth factor (VEGF) expression is associated with diabetes and its vascular complications, but the mechanisms leading to higher VEGF levels are still not clear. To the best of our knowledge, there are no data to show the associations between fetuin-A and VEGF in patients with type 2 diabetes. Therefore, the aim of this study is to investigate the relationship between serum fetuin-A concentrations and serum VEGF levels in patients with type 2 diabetes. We recruited 345 patients with newly diagnosed type 2 diabetes. Serum fetuin-A concentrations and serum VEGF levels were measured using enzyme-linked immunosorbent assay (ELISA) method. In this study, there was a significant positive correlation between serum fetuin-A concentrations and serum VEGF levels (r=0.223, P<0.001), and the correlation remained significant even after adjustment for other confounding factors in the multivariate regression model (β=0.151, P=0.006). Mantel-Haenszel (M-H) stratified analysis showed that the degree of association of high concentrations of fetuin-A with high levels of VEGF is higher than that with low levels of VEGF (odds ratio of M-H [ORM-H], 2.938; 95% confidence interval [CI], 1.896-4.553). In addition, this study showed that both fetuin-A and VEGF were positively associated with fasting plasma glucose (FPG), glycated hemoglobin A1c (HbA1c) and C-reactive protein (CRP). These data suggested that serum fetuin-A concentrations were positively associated with serum VEGF levels in patients with newly diagnosed type 2 diabetes.

The relationship of circulating fetuin-a with liver histology and biomarkers of systemic inflammation in nondiabetic subjects with nonalcoholic fatty liver disease

BACKGROUND/AIMS

Fetuin-A, a glycoprotein with anti-inflammatory properties, plays an important role in counter-regulating inflammatory responses. It has also been associated with insulin resistance and metabolic syndrome. We aimed to investigate circulating concentrations of fetuin-A and its possible association with hepatic and systemic inflammation in nondiabetic subjects with nonalcoholic fatty liver disease (NAFLD).

PATIENTS AND METHODS

We included 105 nondiabetic male subjects with NAFLD [nonalcoholic steatohepatitis (NASH, n = 86) and simple steatosis (SS, n = 19)]. Plasma levels of fetuin-A and markers of inflammation [high-sensitive C reactive protein (hsCRP), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and adiponectin] were measured by enzyme-linked immunosorbent assay method. Insulin sensitivity was determined by homeostasis model assessment of insulin resistance (HOMA-IR) index.

RESULTS

Fetuin-A was negatively correlated with age (r = -0.27, P = 0.006), however there was no association between fetuin-A and body mass index, waist circumference (WC), glucose, insulin, HOMA-IR, lipid parameters, and inflammatory markers. In addition, no significant association was observed between fetuin-A and histological findings including liver fibrosis.

CONCLUSION

This study demonstrated that plasma fetuin-A levels are not correlated with the hepatic histology and systemic markers of inflammation in nondiabetic subjects with NAFLD. Our data also suggested that age is significantly associated with fetuin-A in this clinically relevant condition.

Serum fetuin-A concentration predicts glycaemic outcomes in people with prediabetes: a prospective study from eastern India

AIM

To evaluate the role of fetuin-A levels in predicting glycaemic outcomes (progression to diabetes or reversion to normoglycaemia) in people with prediabetes.

METHODS

A total of 2119 people were screened, of whom 144 people with prediabetes, 50 people with normoglycaemia and 66 people with newly diagnosed diabetes underwent estimation of fasting insulin, fetuin-A, interleukin-6, interleukin-1β, tumour necrosis factor-α, lipid and 25-hydroxyvitamin-D levels and assessment of non-alcoholic fatty liver disease using ultrasonography and the fatty liver index. People with prediabetes were followed and analysed according to glycaemic outcome and quartile of fetuin-A level.

RESULTS

Fetuin-A, interleukin-1β, interleukin-6, tumour necrosis factor-α and triglyceride levels and presence of non-alcoholic fatty liver disease increased across the glycaemic spectrum and were highest in people with diabetes. A total of 32 people with prediabetes reverted to normoglycaemia, 23 progressed to diabetes and 65 remained with prediabetes over a mean ± sd follow-up of 32.12 ± 8.4 months. People progressing to diabetes had higher baseline glycaemia rates, fetuin-A levels, interleukin-1β levels, fatty liver index scores and prevalence of non-alcoholic fatty liver disease and lower 25-hydroxyvitamin-D levels. People with prediabetes in the highest fetuin-A quartile had the highest risk of progression to diabetes (relative risk 2.68, 95% CI 0.95-7.55; P = 0.06) and the lowest rate of reversion to normoglycaemia (relative risk 0.27, 95% CI 0.08-0.85; P = 0.03). Fetuin-A levels correlated with interleukin-1β levels (r = 0.420; P < 0.001), interleukin-6 levels (r = 0.231; P = 0.022) and fatty liver index scores (r = 0.319; P < 0.001). Cox regression showed that higher fetuin-A levels and higher BMI and lower 25-hydroxyvitamin-D levels were predictive of lower rates of reversion to normoglycaemia. Age, triglyceride levels, and interleukin-6 and interleukin-1β levels were predictive of progression to diabetes.

CONCLUSIONS

Increased fetuin-A level has an adverse impact on glycaemic outcomes in prediabetes. This study highlights the importance of fetuin-A as a predictor of glycaemic outcomes in prediabetes.

Circulating alanine transaminase (ALT) and γ-glutamyl transferase (GGT), but not fetuin-A, are associated with metabolic risk factors, at baseline and at two-year follow-up: the prospective Cyprus Metabolism Study

OBJECTIVE

To comparatively evaluate traditional liver tests and fetuin A as predictors of cardiometabolic risk, we studied associations between serum alanine transaminase (ALT), γ-glutamyl transferase (GGT), aspartate aminotransferase (AST) and fetuin-A and anthropometric, metabolic, and cardiovascular parameters cross-sectionally at baseline, and prospectively, after 2-years of follow-up.

RESEARCH DESIGN AND METHODS

616 randomly enrolled young healthy participants in the Cyprus Metabolism Study, including all 93 subjects who participated in the follow-up study 2 years after baseline assessment, were included in this study.

RESULTS

In the cross-sectional study, serum ALT and GGT were strongly correlated with anthropometric, cardiovascular, and metabolic variables, while serum AST was only correlated with waist circumference and waist-to-hip ratio. Fetuin-A was correlated with anthropometric variables, systolic blood pressure (SBP), insulin, and homeostasis model of assessment-insulin resistance (HOMA-IR) in the unadjusted model. In the fully adjusted model, both serum ALT and GGT levels remained positively correlated with total and low-density lipoprotein (LDL) cholesterol. GGT levels also remained correlated with triglycerides. ALT levels remained strongly positively correlated with insulin (r=0.17, p<.0001) and HOMA-IR (r=0.16, p=0.0001). Serum fetuin-A levels were no longer significantly correlated with any variables. Prospectively, ALT and GGT were predictors of anthropometric variables and LDL cholesterol, while baseline levels of AST and fetuin-A were not predictors of any variables at 2-year follow-up.

CONCLUSIONS

We confirmed associations of ALT and GGT levels but failed to demonstrate an independent association between fetuin-A and cardiometabolic risk factors in young healthy men. Traditional liver tests (LFTs) are thus better than fetuin-A predictors of metabolic risk factors cross-sectionally and prospectively in young healthy adults.

Lower fetuin-A, retinol binding protein 4 and several metabolites after gastric bypass compared to sleeve gastrectomy in patients with type 2 diabetes

Background

Bypass of foregut secreted factors promoting insulin resistance is hypothesized to be one of the mechanisms by which resolution of type 2 diabetes (T2D) follows roux-en-y gastric bypass (GBP) surgery.

Aim

To identify insulin resistance-associated proteins and metabolites which decrease more after GBP than after sleeve gastrectomy (SG) prior to diabetes remission.

Methods

Fasting plasma from 15 subjects with T2D undergoing GBP or SG was analyzed by proteomic and metabolomic methods 3 days before and 3 days after surgery. Subjects were matched for age, BMI, metformin therapy and glycemic control. Insulin resistance was calculated using homeostasis model assessment (HOMA-IR). For proteomics, samples were depleted of abundant plasma proteins, digested with trypsin and labeled with iTRAQ isobaric tags prior to liquid chromatography-tandem mass spectrometry analysis. Metabolomic analysis was performed using gas chromatography-mass spectrometry. The effect of the respective bariatric surgery on identified proteins and metabolites was evaluated using two-way analysis of variance and appropriate post-hoc tests.

Results

HOMA-IR improved, albeit not significantly, in both groups after surgery. Proteomic analysis yielded seven proteins which decreased significantly after GBP only, including Fetuin-A and Retinol binding protein 4, both previously linked to insulin resistance. Significant decrease in Fetuin-A and Retinol binding protein 4 after GBP was confirmed using ELISA and immunoassay. Metabolomic analysis identified significant decrease of citrate, proline, histidine and decanoic acid specifically after GBP.

Conclusion

Greater early decrease was seen for Fetuin-A, Retinol binding protein 4, and several metabolites after GBP compared to SG, preceding significant weight loss. This may contribute to enhanced T2D remission observed following foregut bypass procedures.

[The role of fetuin-A in cardiovascular diseases]

Fetuin-A (also known as α2-Heremans-Schmid glycoprotein) is a multifunctional molecule secreted by the liver. It is a negative acute phase reactant with a debated role in subclinical inflammation. Fetuin-A is an inhibitor of the insulin receptor and its serum level correlates with insulin resistance. The protein has been implicated in adipocyte dysfunction and it is associated with obesity and non-alcoholic fatty liver disease. Although all these properties seem to promote atherosclerosis, the role of fetuin-A in cardiovascular diseases is more complex. As a natural inhibitor of tissue and vascular calcification, fetuin-A also acts as a protective factor in atherosclerosis. The potential role and prognostic value of fetuin-A in arterial calcification and cardiovascular diseases is discussed in this review, along with explanations for seemingly contradicting results in the literature and possible directions for future research.

Fetuin-A mRNA expression is elevated in NASH compared with NAFL patients

Fetuin-A is a pro-inflammatory protein expressed by hepatocytes. Its course in morbidly obese patients with NAFLD (non-alcoholic fatty liver disease) following weight loss by BAS (bariatric surgery) has not been fully elucidated yet. In the present study, we prospectively examined the effects of weight loss on various metabolic factors at 4 weeks and 6 months after surgery. Blood and liver tissues were retrieved from 108 morbidly obese NAFLD patients before/during BAS, and 50 of these individuals met the criteria for NASH (non-alcoholic steatohepatitis). Fetuin-A expression was measured by qPCR (quantitative real-time PCR), Western blotting and immunohistochemistry. Hepatocyte apoptosis was quantified via M30 (caspase-cleaved cytokeratin-18 fragments). Plasma concentrations of adiponectin and fetuin-A were determined by ELISA. Serum-derived parameters were additionally taken at 4 weeks and 6 months post-operatively. In addition, primary human hepatocytes were treated with NEFA (non-esterified fatty acid) to investigate changes in fetuin-A. BMI (body mass index) decreased significantly from 53.0±1.1 to 36.4±1.9 kg/m2 in the NAFL group and from 53.3±1.1 to 37.6±1.2 kg/m2 in the NASH group (P<0.0001) at 6 months post-surgery. This was associated with diminishing M30 and M65 (total cytokeratin-18) levels over 6 months after surgery. Adiponectin levels increased continuously in NASH patients, whereas NAFL patients plateaued at 4 weeks post-operatively. Hepatic fetuin-A mRNA and protein expression was elevated before surgery-induced weight loss. However, plasma concentrations of fetuin-A increased signficantly in NASH patients 4 weeks post-operatively. Treatment of hepatocytes with NEFA led to up-regulation of fetuin-A expression. BAS probably has a beneficial effect on NAFLD, as indicated by reduced hepatocyte apoptosis and improved adipokine profiles. In addition, fetuin-A expression is more prominent in NASH.

Fetuin-A is linked to improved glucose tolerance after short-term exercise training in nonalcoholic fatty liver disease

Fetuin-A is synthesized in the liver and may be associated with nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. Lifestyle-induced weight loss reduces fetuin-A, but the effect of exercise alone is unknown. We determined the effect of short-term exercise training on plasma fetuin-A in 13 (50.5 ± 3.4 yr) obese adults (body mass index, 33.3 ± 0.9 kg/m(2)) with clinically diagnosed NAFLD. Subjects participated in 7 days of supervised exercise training (60 min/day at ∼85% maximum heart rate) and were instructed to maintain their normal caloric and macronutrient intake. Insulin resistance was assessed by an oral glucose tolerance test. Hepatic triglyceride content (HTGC) was determined by proton MRI. We used C2C12 skeletal muscle cells to examine the direct effect of fetuin-A on 2-deoxyglucose uptake, insulin signaling [phosphorylation of Akt and AS160 (pAkt and pAS160, respectively)], and glucose transporter-4 (GLUT-4) translocation. Insulin resistance was reduced by 29% (P < 0.05), and glucose area under the curve (AUC) was decreased by 13% (P < 0.01) after the 7 days of exercise. Furthermore, circulating fetuin-A was decreased by 11% (4.2 ± 03 vs. 3.6 ± 0.2 nM; P < 0.02), and this change correlated with reduced insulin resistance (r = 0.62; P < 0.04) and glucose AUC (r = 0.58; P < 0.04). Importantly, the exercise program did not change body weight (P = 0.12), HTGC (P = 0.73), or aerobic capacity (P = 0.14). In vitro experiments revealed that fetuin-A decreased skeletal muscle glucose uptake by downregulating pAkt and pAS160 and subsequent GLUT-4 translocation to the plasma membrane. Together, our findings highlight a role for fetuin-A in skeletal muscle insulin resistance and suggest that part of the exercise-induced improvement in glucose tolerance in patients with NAFLD may be due to lowering fetuin-A.

Sex-specific association of fetuin-A with type 2 diabetes in older community-dwelling adults: the Rancho Bernardo study

OBJECTIVE

This study evaluated the sex-specific association of plasma fetuin-A levels with prevalent and incident type 2 diabetes in community-dwelling older adults.

RESEARCH DESIGN AND METHODS

Participants were 684 men and 1,058 women (median age, 71 years) whose fetuin-A levels, diabetes prevalence, and diabetes risk factors were evaluated in 1992-1996. The participants were followed for incident diabetes through 2010 (median follow-up, 9 years).

RESULTS

Women with impaired glucose tolerance had elevated fetuin-A levels compared with women with normal glucose tolerance (P = 0.019), but fetuin-A levels were not elevated in women with impaired fasting glucose. Fetuin-A did not vary by glucose tolerance status in men. There were significant interactions of fetuin-A by sex for prevalent (P = 0.007) and incident (P = 0.020) diabetes. For women, each SD (0.10 g/L) higher fetuin-A level was associated with a higher odds of prevalent diabetes (odds ratio [OR] 1.79, 95% CI 1.47-2.17) and greater risk of incident diabetes (hazard ratio [HR] 1.66, 95% CI 1.18-2.34), adjusting for age and estrogen therapy. These associations were not materially altered by adjustment for diabetes risk factors but were attenuated by adjusting for postchallenge glucose levels. Among men, although positive associations with prevalent (OR 1.15 [0.94-1.41]) and incident (HR 1.24 [0.93-1.65]) diabetes were suggested in age-adjusted models, risk estimates attenuated to one after multivariable adjustment.

CONCLUSIONS

Higher fetuin-A concentrations were independently associated with an increased risk of developing type 2 diabetes in older women but were not related to diabetes risk in older men. Fetuin-A may provide novel insights into mechanisms underlying sex differences in glucose homeostasis and diabetes risk in old age.

Interactions among bone, liver, and adipose tissue predisposing to diabesity and fatty liver

Growing epidemiological evidence connects obesity and its complications, including metabolic syndrome, diabetes, and nonalcoholic fatty liver disease (NAFLD) to reduced bone health and osteoporosis. Parallel to human studies, experimental data disclosed a complex network of interaction among adipose tissue, the liver, and the bone, which reciprocally modulate the function of each other. The main mediators of such crosstalk include hormonal/cytokine signals from the bone (osteopontin, osteocalcin, and osteoprotegerin), the liver (fetuin-A), and adipose tissue [leptin, tumor necrosis factor-α (TNF-α), and adiponectin]. Dysregulation of this network promotes the development of diabesity, NAFLD, and osteoporosis. We will review recent advances in understanding the mechanisms of bone-liver-adipose tissue interaction predisposing to obesity, diabetes, NAFLD, and osteoporosis and their potential clinical implications.

Multiple mechanisms of GW-9508, a selective G protein-coupled receptor 40 agonist, in the regulation of glucose homeostasis and insulin sensitivity

Activation of G protein-coupled receptor 40 (GPR40) by agonists increases insulin release in isolated islets, whereas it is inconclusive whether GPR40 antagonists decrease blood glucose and increase insulin sensitivity. Although some clinical trials indicated that administration of a GPR40 agonist shows benefits in the regulation of blood glucose homeostasis, the pharmacological mechanisms of this receptor in the improvement of glycemic control remain unclear. Therefore, we used a selective GPR40 agonist, GW-9508, to clarify the role of GPR40 in the regulation of blood glucose. Bolus intraperitoneal injection of GW-9508 in mice showed a slight decrease in blood glucose, with an increase in plasma insulin levels under glucose stimuli. However, long-term treatment with low doses of GW-9508 in high-fat diet-induced (HFD) diabetic mice decreased blood glucose with decreased plasma insulin significantly and improved glucose intolerance and insulin resistance. Using small interfering ribonucleic acid to delete GPR40 in HepG2 cells, we demonstrated that GW-9508 reversed palmitate-induced insulin signaling impairment through a GPR40-dependent pathway. We also found that GW-9508 activates the Akt/GSK-3β pathway to increase glycogen levels in HepG2 cells. Furthermore, administration of GW-9508 decreased the hepatic expression of fetuin-A in HFD mice significantly and regulated high-glucose- or palmitate-induced fetuin-A expression to increase insulin sensitivity through a GPR40/PLC/PKC pathway in HepG2 cells. Taken together, GW-9508 exerts a partial agonist effect to regulate blood glucose through multiple mechanisms. Investigation of chemicals that act on GPR40 might be a new strategy for the treatment of diabetes.

Ahsg-fetuin blocks the metabolic arm of insulin action through its interaction with the 95-kD β-subunit of the insulin receptor

We previously have shown that Ahsg, a liver glycoprotein, inhibits insulin receptor (InsR) tyrosine kinase (TK) activity and the ERK1/2 mitogenic signaling arm of insulin signaling. Here we show that Ahsg blocks insulin-stimulated GLUT4 translocation and Akt activation in intact cells (mouse myoblasts). Furthermore, Ahsg inhibits InsR autophosphorylation of highly-purified insulin holoreceptors in a cell-free, ATP-dependent system, with an IC50 within the range of single-chain Ahsg concentrations in human serum. Binding of (125)I-insulin to living cells overexpressing the InsR shows a dissociation constant (KD) of 250pM, unaltered in the presence of 300 nM Ahsg. A mutant InsR cDNA encoding the signal peptide, the β-subunit and the furin processing site, but deleting the α-subunit, was stably expressed in HEK293 cells. Treatment with peroxovanadate, but not insulin, dramatically increased the 95 kD β-subunit tyrosine phosphoryation. The level of tyrosine phosphorylation of the 95-kD β-subunit can be driven down sharply by treatment of living HEK293 transfectant cells with physiological doses of Ahsg. Treatment of myogenic cells with Ahsg blunts insulin-stimulated InsR autophosphorylation and AKT phosphorylation. Taken together, we show that Ahsg antagonizes the metabolic functions initiated by InsR activation without interference in insulin binding. The experiments suggest a direct interaction of Ahsg with the InsR ectodomain β-subunit in a mode that does not significantly alter the high-affinity binding of insulin to the holoreceptor's two complementing α-subunits.

Plasma levels of fetuin-A and hepatic enzymes and risk of type 2 diabetes in women in the U.S

Fetuin-A interferes with insulin action in animal studies, but data on fetuin-A and diabetes risk in humans are sparse and the role of nonalcoholic fatty liver disease in this association is unknown. From 2000 to 2006, we prospectively identified 470 matched incident diabetes case-control pairs in the Nurses' Health Study, for whom levels of plasma fetuin-A, alanine transaminase (ALT), and γ-glutamyltranspeptidase (GGT) were measured. After multivariate adjustment for covariates, including ALT and GGT, the odds ratio (OR) (95% CI) comparing extreme fetuin-A quintiles was 1.81 (1.07-3.06) (P for trend = 0.009). A mediational analysis showed that this positive association was largely (79.9%) explained by fasting insulin and hemoglobin A(1c) levels; after further adjustment of these factors, the OR (95% CI) comparing extreme quintiles was attenuated to 1.09 (0.56-2.10) (P for trend = 0.42). In addition, liver enzymes did not modify this association (P for interaction = 0.91 for ALT and 0.58 for GGT). When results from this study were pooled with those in three prior prospective investigations of the same association, a consistent, positive association was observed between high fetuin-A levels and diabetes risk: the relative risk (95% CI) comparing high versus low fetuin-A levels was 1.69 (1.39-2.05) (P for heterogeneity = 0.45). These findings suggest that plasma fetuin-A levels were independently associated with higher risk of developing type 2 diabetes.

Fetuin-A levels in hyperthyroidism

OBJECTIVE

Fetuin-A is a protein secreted from the liver that inhibits arterial calcification deposition and can contribute to insulin resistance. Hyperthyroidism is also associated with insulin resistance. It is not known whether hyperthyroidism has an effect on fetuin-A levels.

METHODS

We measured fetuin-A levels and homeostasis model of assessment-insulin resistance before hyperthyroidism treatment was initiated and after euthyroidism was achieved. A total of 42 patients diagnosed with hyperthyroidism were enrolled in this study. Fetuin-A, insulin, high-sensitivity C-reactive protein, fasting blood glucose, free T3 (fT3), free T4 (fT4), and thyrotropin were measured before and after euthyroidism was established.

RESULTS

Basal fasting blood glucose, high-sensitivity C-reactive protein, insulin, c-peptide, homeostasis model of assessment-insulin resistance, fT3, fT4 and fetuin-A levels were significantly decreased after euthyroidism was achieved (Table 1). Basal fasting blood glucose (r:0.407, p:0.008), high-sensitivity C-reactive protein (r:0.523, p<0.0001), insulin (r:0.479, p:0.001), homeostasis model of assessment-insulin resistance (r:0.541, p<0.0001), fT3 (r:0.492, p:0.001) and fT4 (r:0.473, p:0.002) were positively correlated with basal fetuin-A levels. Basal thyrotropin levels were significantly negatively correlated (r:-0.553, p<0.0001) with basal fetuin-A levels.

CONCLUSION

Our findings suggest that hyperthyroidism influences fetuin-A levels.

Increased fetuin-A concentrations in impaired glucose tolerance with or without nonalcoholic fatty liver disease, but not impaired fasting glucose

CONTEXT

Fetuin-A, a liver-derived glycoprotein that impairs insulin signaling, is associated with nonalcoholic fatty liver disease (NAFLD), diabetes, and the risk of cardiovascular diseases. Both prediabetes and NAFLD are associated with increased cardiovascular risk, and their concurrence significantly impairs hepatic and adipose tissue insulin sensitivity.

OBJECTIVE

Our objective was to investigate the relationship between serum fetuin-A levels and prediabetes in subjects with or without NAFLD.

DESIGN

This was a cross-sectional case-control study.

PATIENTS

A total of 510 age- and sex-matched subjects with normal glucose tolerance (NGT), impaired fasting glucose (IFG), and impaired glucose tolerance (IGT) with or without NAFLD were recruited. Each subject was assessed by abdominal ultrasound to diagnose NAFLD.

MAIN OUTCOME MEASURES

Serum fetuin-A concentrations were compared between groups. The association with clinico-metabolic parameters was examined.

RESULTS

The presence of NAFLD significantly increases fetuin-A levels in subjects with NGT and prediabetes. As compared with NGT, IGT, but not IFG, significantly increases fetuin-A levels in subjects with or without NAFLD. Serum fetuin-A concentrations were positively related to postload 2-h glucose, body mass index, triglyceride, and homeostasis model assessment of insulin resistance but negatively associated with age, high-density lipoprotein cholesterol, and adiponectin. In multiple regression analysis, age, IGT vs. NGT, and IGT with NAFLD vs. NGT were independently associated with fetuin-A levels after adjustment for cardiovascular risk factors and adiponectin.

CONCLUSIONS

IGT with or without NAFLD was independently associated with fetuin-A levels after adjustment for cardiometabolic risk factors. The elevated fetuin-A levels could have a clinical implication in the increased cardiovascular risk and insulin resistance associated with NAFLD and IGT.