Treatment with atorvastatin reduces serum adipocyte-fatty acid binding protein value in patients with hyperlipidaemia

Fatty Acid-Binding Protein 4-Mediated Regulation Is Pivotally Involved in Retinal Pathophysiology: A Review

Fatty acid-binding proteins (FABPs), a family of lipid chaperone molecules that are involved in intracellular lipid transportation to specific cellular compartments, stimulate lipid-associated responses such as biological signaling, membrane synthesis, transcriptional regulation, and lipid synthesis. Previous studies have shown that FABP4, a member of this family of proteins that are expressed in adipocytes and macrophages, plays pivotal roles in the pathogenesis of various cardiovascular and metabolic diseases, including diabetes mellitus (DM) and hypertension (HT). Since significant increases in the serum levels of FABP4 were detected in those patients, FABP4 has been identified as a crucial biomarker for these systemic diseases. In addition, in the field of ophthalmology, our group found that intraocular levels of FABP4 (ioFABP4) and free fatty acids (ioFFA) were substantially elevated in patients with retinal vascular diseases (RVDs) including proliferative diabetic retinopathy (PDR) and retinal vein occlusion (RVO), for which DM and HT are also recognized as significant risk factors. Recent studies have also revealed that ioFABP4 plays important roles in both retinal physiology and pathogenesis, and the results of these studies have suggested potential molecular targets for retinal diseases that might lead to future new therapeutic strategies.

Circulating AFABP, FGF21, and PEDF Levels as Prognostic Biomarkers of Sight-threatening Diabetic Retinopathy

CONTEXT

Adipocyte fatty acid-binding protein (AFABP), fibroblast growth factor 21 (FGF21), and pigment epithelium-derived factor (PEDF) are 3 diabetes-related biomarkers whose circulating levels had been shown to associate with nephropathy progression in Chinese patients with type 2 diabetes.

OBJECTIVE

Here, we evaluated and compared their prospective associations with the development of sight-threatening DR (STDR), another important diabetic microvascular complication.

METHODS

Baseline serum AFABP, PEDF, and FGF21 levels were measured in 4760 Chinese individuals with type 2 diabetes and without STDR at baseline. The associations of these biomarkers with incident STDR were analyzed using Cox regression analysis.

RESULTS

Among these 4760 participants (mean diabetes duration of 11 years and ≥ 50% with nonproliferative DR at baseline), 172 participants developed STDR over a median follow-up of 8.8 years. Participants with incident STDR had comparable baseline serum FGF21 levels but significantly higher baseline serum AFABP and PEDF levels (both P < .001) than those without. However, in multivariable Cox regression analysis, only serum AFABP remained independently associated with incident STDR (hazard ratio 1.28; 95% CI, 1.05-1.55; P = .013). The addition of serum AFABP to a clinical model of conventional STDR risk factors including diabetes duration, glycemic control, albuminuria, and baseline DR status significantly improved the c statistics (P < .001), net reclassification index (P = .0027), and integrated discrimination index (P = .033) in predicting incident STDR among participants without DR or with mild DR at baseline.

CONCLUSION

Among the 3 diabetes-related biomarkers, serum AFABP level appeared to be a more clinically useful biomarker for predicting incident STDR in type 2 diabetes.

Valproate-Induced Metabolic Syndrome

Valproic acid (VPA) and its salts (sodium calcium magnesium and orotic) are psychotropic drugs that are widely used in neurology and psychiatry. The long-term use of VPA increases the risk of developing adverse drug reactions (ADRs), among which metabolic syndrome (MetS) plays a special role. MetS belongs to a cluster of metabolic conditions such as abdominal obesity, high blood pressure, high blood glucose, high serum triglycerides, and low serum high-density lipoprotein. Valproate-induced MetS (VPA-MetS) is a common ADR that needs an updated multidisciplinary approach to its prevention and diagnosis. In this review, we consider the results of studies of blood (serum and plasma) and the urinary biomarkers of VPA-MetS. These metabolic biomarkers may provide the key to the development of a new multidisciplinary personalized strategy for the prevention and diagnosis of VPA-MetS in patients with neurological diseases, psychiatric disorders, and addiction diseases.

Targeting Fatty Acid-Binding Protein 4 Improves Pathologic Features of Aortic Stenosis

Aortic stenosis (AS) is a fibrocalcific disease of the aortic valves (AVs). Sex-differences in AS pathophysiology have recently been described. High levels of fatty acid-binding protein 4 (FAPB4) in atherosclerotic plaques have been associated with increased local inflammation, endothelial dysfunction, and plaque vulnerability. FABP4 pharmacological blockade has been shown to be effective for the treatment of atherosclerosis by modulating metabolic and inflammatory pathways. We aimed to analyze the sex-specific expression of FABP4 in AS and its potential role as a therapeutic target. A total of 226 patients (61.5% men) with severe AS undergoing surgical AV replacement were recruited. The FABP4 levels were increased in the AVs of AS patients compared to the control subjects, showing greater expression in the fibrocalcific regions. Male AVs exhibited higher levels of FABP4 compared to females, correlating with markers of inflammation (IL-6, Rantes), apoptosis (Bax, caspase-3, Bcl-2), and calcification (IL-8, BMP-2 and BMP-4). VICs derived from AS patients showed the basal expression of FABP4 in vitro. Osteogenic media induced upregulation of intracellular and secreted FABP4 levels in male VICs after 7 days, along with increased levels of inflammatory, pro-apoptotic, and osteogenic markers. Treatment with BMS309403, a specific inhibitor of FABP4, prevented from all of these changes. Thus, we propose FABP4 as a new sex-specific pharmacological therapeutic target in AS.

Interplay between Fatty Acid Binding Protein 4, Fetuin-A, Retinol Binding Protein 4 and Thyroid Function in Metabolic Dysregulation

Signalling between the tissues integrating synthesis, transformation and utilization of energy substrates and their regulatory hormonal axes play a substantial role in the development of metabolic disorders. Interactions between cytokines, particularly liver derived hepatokines and adipokines, secreted from adipose tissue, constitute one of major areas of current research devoted to metabolic dysregulation. The thyroid exerts crucial influence on the maintenance of basal metabolic rate, thermogenesis, carbohydrate and lipid metabolism, while its dysfunction promotes the development of metabolic disorders. In this review, we discuss the interplay between three adipokines: fatty acid binding protein type 4, fetuin-A, retinol binding protein type 4 and thyroid hormones, that shed a new light onto mechanisms underlying atherosclerosis, cardiovascular complications, obesity, insulin resistance and diabetes accompanying thyroid dysfunction. Furthermore, we summarize clinical findings on those cytokines in the course of thyroid disorders.

Adipose-Derived Lipid-Binding Proteins: The Good, the Bad and the Metabolic Diseases

Adipose tissue releases a large range of bioactive factors called adipokines, many of which are involved in inflammation, glucose homeostasis and lipid metabolism. Under pathological conditions such as obesity, most of the adipokines are upregulated and considered as deleterious, due to their pro-inflammatory, pro-atherosclerotic or pro-diabetic properties, while only a few are downregulated and would be designated as beneficial adipokines, thanks to their counteracting properties against the onset of comorbidities. This review focuses on six adipose-derived lipid-binding proteins that have emerged as key factors in the development of obesity and diabetes: Retinol binding protein 4 (RBP4), Fatty acid binding protein 4 (FABP4), Apolipoprotein D (APOD), Lipocalin-2 (LCN2), Lipocalin-14 (LCN14) and Apolipoprotein M (APOM). These proteins share structural homology and capacity to bind small hydrophobic molecules but display opposite effects on glucose and lipid metabolism. RBP4 and FABP4 are positively associated with metabolic syndrome, while APOD and LCN2 are ubiquitously expressed proteins with deleterious or beneficial effects, depending on their anatomical site of expression. LCN14 and APOM have been recently identified as adipokines associated with healthy metabolism. Recent findings on these lipid-binding proteins exhibiting detrimental or protective roles in human and murine metabolism and their involvement in metabolic diseases are also discussed.

A-FABP in Metabolic Diseases and the Therapeutic Implications: An Update

Adipocyte fatty acid-binding protein (A-FABP), which is also known as ap2 or FABP4, is a fatty acid chaperone that has been further defined as a fat-derived hormone. It regulates lipid homeostasis and is a key mediator of inflammation. Circulating levels of A-FABP are closely associated with metabolic syndrome and cardiometabolic diseases with imminent diagnostic and prognostic significance. Numerous animal studies have elucidated the potential underlying mechanisms involving A-FABP in these diseases. Recent studies demonstrated its physiological role in the regulation of adaptive thermogenesis and its pathological roles in ischemic stroke and liver fibrosis. Due to its implication in various diseases, A-FABP has become a promising target for the development of small molecule inhibitors and neutralizing antibodies for disease treatment. This review summarizes the clinical and animal findings of A-FABP in the pathogenesis of cardio-metabolic diseases in recent years. The underlying mechanism and its therapeutic implications are also highlighted.

Detection of significantly high vitreous concentrations of fatty acid-binding protein 4 in patients with proliferative diabetic retinopathy

The fatty acid-binding protein4 (FABP4) and vascular endothelial growth factor A (VEGFA) play key roles in the metabolic and cardiovascular diseases, and proliferative diabetic retinopathy (PDR), respectively. To identify FABP4 in vitreous fluid in PDR, vitreous concentrations of FABP4 (V-FABP4) and VEGFA (V-VEGFA) from PDR (n = 20) and non-PDR (n = 20) patients were determined by Enzyme-Linked ImmunoSorbent Assays. The data, which included height and weight, systemic blood pressures, several blood biochemical parameters and blood flow at the optic nerve head (ONH) by laser speckle flowgraphy (LSFG) were collected. The levels of V-FABP4 and V-VEGFA were significantly higher in PDR patients than in non-PDR patients (P < 0.001) with a high positive correlation (r = 0.72, P < 0.001) between them. The findings were not affected by body mass index values and the presence of vitreous hemorrhaging. Among the clinical parameters, V-FABP4 correlated positively with creatinine and negatively with age and aspartate transaminase (AST) levels, while V-VEGFA correlated positively with fasting plasma glucose and hemoglobin A1c (HbA1c) levels but negatively with AST. Multiple regression analyses indicated that V-VEGFA, or V-FABP4, AST and HbA1c were independent predictors of V-FABP4 or V-VEGFA, respectively. Both were negatively correlated, but more evident in V-FABP4, with the ONH ocular blood flow.

Adipocyte-Specific Fatty Acid-Binding Protein (AFABP) and Chemerin in Association with Gestational Diabetes: A Case-Control Study

BACKGROUND

Adipocytokines participate in regulating the inflammatory response in glucose homeostasis and type 2 diabetes. However, among these peptides, the role of adipocyte-specific fatty-acid-binding protein (AFABP), chemerin, and secreted protein acidic and rich in cysteine (SPARC) in gestational diabetes (GDM) has not been fully investigated.

METHOD

The maternal fasting level of adipocytokines of 53 subjects with GDM and 43 normal pregnant (NGDM) was measured using multiplex immunoassay at 24-28 weeks, before delivery, immediate postpartum, and 2-6 months postpuerperium.

RESULTS

Higher levels of AFABP were associated with a 3.7-fold higher risk of GDM. Low chemerin levels were associated with a 3.6-fold higher risk of GDM. Interleukin-10 (IL-10) was inversely associated with the risk of GDM. SPARC had no association with GDM. AFABP was directly correlated to interleukin-6 (r = 0.50), insulin resistance index (r = 0.26), and body mass index (r = 0.28) and inversely correlated to C-reactive protein (r = -0.27). Chemerin levels were directly and strongly correlated with IL-10 (r = 0.41) and interleukin-4 (r = 0.50) and inversely correlated to insulin resistance index (r = -0.23) in GDM but not NGDM. In the longitudinal assessment, there were no significant differences in AFABP and chemerin concentrations of both studied groups.

CONCLUSION

AFABP and chemerin were associated with a higher risk of GDM. These adipocytokines were related to insulin resistance, body mass index, and inflammation in pregnant women diagnosed with GDM.

Adipocyte Fatty Acid-Binding Protein, Cardiovascular Diseases and Mortality

It has been increasingly recognized that inflammation plays an important role in the pathogenesis of cardiovascular disease (CVD). In obesity, adipose tissue inflammation, especially in the visceral fat depots, contributes to systemic inflammation and promotes the development of atherosclerosis. Adipocyte fatty acid-binding protein (AFABP), a lipid chaperone abundantly secreted from the adipocytes and macrophages, is one of the key players mediating this adipose-vascular cross-talk, in part via its interaction with c-Jun NH2-terminal kinase (JNK) and activator protein-1 (AP-1) to form a positive feedback loop, and perpetuate inflammatory responses. In mice, selective JNK inactivation in the adipose tissue significantly reduced the expression of AFABP in their adipose tissue, as well as circulating AFABP levels. Importantly, fat transplant experiments showed that adipose-specific JNK inactivation in the visceral fat was sufficient to protect mice with apoE deficiency from atherosclerosis, with the beneficial effects attenuated by the continuous infusion of recombinant AFABP, supporting the role of AFABP as the link between visceral fat inflammation and atherosclerosis. In humans, raised circulating AFABP levels are associated with incident metabolic syndrome, type 2 diabetes and CVD, as well as non-alcoholic steatohepatitis, diabetic nephropathy and adverse renal outcomes, all being conditions closely related to inflammation and enhanced CV mortality. Collectively, these clinical data have provided support to AFABP as an important adipokine linking obesity, inflammation and CVD. This review will discuss recent findings on the role of AFABP in CVD and mortality, the possible underlying mechanisms, and pharmacological inhibition of AFABP as a potential strategy to combat CVD.

Elevated circulating FABP4 concentration predicts cardiovascular death in a general population: a 12-year prospective study

Fatty acid-binding protein 4 (FABP4) is secreted from adipose tissue and acts as an adipokine, and an elevated circulating FABP4 level is associated with metabolic disorders and atherosclerosis. However, little is known about the causal link between circulating FABP4 level and mortality in a general population. We investigated the relationship between FABP4 concentration and mortality including cardiovascular death during a 12-year period in subjects of the Tanno-Sobetsu Study, a population-based cohort (n = 721, male/female: 302/419). FABP4 concentration at baseline was significantly higher in female subjects than in male subjects. All-cause death occurred in 123 (male/female: 74/49) subjects, and 34 (male/female: 20/14) and 42 (male/female: 26/16) subjects died of cardiovascular events and cancer, respectively. When divided into 3 groups according to tertiles of FABP4 level at baseline by sex (T1–T3), Kaplan–Meier survival curves showed that there were significant differences in rates of all-cause death and cardiovascular death, but not cancer death, among the groups. Multivariable Cox proportional hazard model analysis with a restricted cubic spline showed that hazard ratio (HR) for cardiovascular death, but not that for all-cause death, significantly increased with a higher FABP4 level at baseline after adjustment of age and sex. The risk of cardiovascular death after adjustment of age, sex, body mass index and levels of brain natriuretic peptide and high-sensitivity C-reactive protein in the 3rd tertile (T3) group (HR: 4.96, 95% confidence interval: 1.20–22.3) was significantly higher than that in the 1st tertile (T1) group as the reference. In conclusion, elevated circulating FABP4 concentration predicts cardiovascular death in a general population.

Fatty-Acid-Binding Protein 4 as a Novel Contributor to Mononuclear Cell Activation and Endothelial Cell Dysfunction in Atherosclerosis

Background—Elevated circulating fatty-acid-binding protein 4 (FABP4) levels may be linked with cardiovascular events. This study aimed to investigate the mechanistic role of FABP4 in atherosclerosis. Methods—We recruited 22 patients with angiographically proven coronary artery disease (CAD) and 40 control subjects. Mononuclear cells (MNCs) and human coronary endothelial cells (HCAECs) were used for in vitro study. Results—Patients with CAD were predominantly male with an enhanced prevalence of hypertension, diabetes, and smoking history. FABP4 concentrations were up-regulated in culture supernatants of MNCs from CAD patients, which were positively correlated with the patients’ age, waist–hip ratio, body mass index, serum creatinine, type 2 diabetes, and the presence of hypertension. The adhesiveness of HCAECs to monocytic cells can be activated by FABP4, which was reversed by an FABP4 antibody. FABP4 blockade attenuated the oxidized low-density lipoprotein (oxLDL)-induced expression of ICAM-1, VCAM-1, and P-selectin. FABP4 impaired the tube formation and migration via the ERK/JNK/STAT-1 signaling pathway. FABP4 suppressed phosphorylation of eNOS and expression of SDF-1 protein, both of which can be reversed by treatment with VEGF. Blockade of FABP4 also improved the oxLDL-impaired cell function. Conclusion—We discovered a novel pathogenic role of FABP4 in MNC activation and endothelial dysfunction in atherosclerosis. FABP4 may be a therapeutic target for modulating atherosclerosis.

Association between adipocyte fatty acid-binding protein with left ventricular remodelling and diastolic function in type 2 diabetes: a prospective echocardiography study

Background

The relationship between adipocyte fatty acid-binding protein (AFABP) and cardiac remodelling has been reported in cross-sectional studies, although with conflicting results. Type 2 diabetes mellitus (T2DM) is associated with left ventricular (LV) hypertrophy and diastolic dysfunction, as well as elevated circulating AFABP levels. Here we investigated prospectively the association between AFABP with the longitudinal changes of cardiac remodelling and diastolic dysfunction in T2DM.

Methods

Circulating AFABP levels were measured in 176 T2DM patients without cardiovascular diseases (CVD) at baseline. All participants received detailed transthoracic echocardiography both at baseline and after 1 year. Multivariable linear and Cox regression analyses were used to evaluate the associations of circulating AFABP levels with changes in echocardiography parameters and incident major adverse cardiovascular events (MACE), respectively.

Results

The median duration between baseline and follow-up echocardiography assessments was 28 months. Higher sex-specific AFABP quartiles at baseline were associated with increase in LV mass and worsening of average E/e′ (all P < 0.01). Multivariable linear regression demonstrated that AFABP in the highest quartile was independently associated with both increase in LV mass (β = 0.89, P < 0.01) and worsening of average E/e′ (β = 0.57, P < 0.05). Moreover, multivariable Cox regression analysis showed that elevated baseline circulating AFABP level independently predicted incident MACE (HR 2.65, 95% CI 1.16–6.05, P < 0.05) after adjustments for age, sex, body mass index, glycated haemoglobin, hypertension, dyslipidemia and presence of chronic kidney disease.

Conclusion

Circulating AFABP level at baseline predicted the development of LV hypertrophy, diastolic dysfunction and MACE in T2DM patients without CVD.

Treatment with anagliptin, a DPP-4 inhibitor, decreases FABP4 concentration in patients with type 2 diabetes mellitus at a high risk for cardiovascular disease who are receiving statin therapy

Background

Fatty acid-binding protein 4 (FABP4) acts as a novel adipokine, and elevated FABP4 concentration is associated with obesity, insulin resistance and atherosclerosis. Dipeptidyl peptidase-4 (DPP-4) inhibitors, a class of antidiabetic drugs, have distinct structures among the drugs, possibly leading to a drug class effect and each drug effect. Sitagliptin, a DPP-4 inhibitor, has been reported to decrease FABP4 concentration in drug-naïve and sulfonylurea-treated patients with type 2 diabetes mellitus. Anagliptin, another DPP-4 inhibitor, was shown to decrease low-density lipoprotein cholesterol (LDL-C) level to a greater extent than that by sitagliptin in the Randomized Evaluation of Anagliptin vs. Sitagliptin On low-density lipoproteiN cholesterol in diabetes (REASON) trial.

Aim and methods

As a sub-analysis study using data obtained from the REASON trial, we investigated the effects of treatment with anagliptin (n = 148, male/female: 89/59) and treatment with sitagliptin (n = 159, male/female: 93/66) for 52 weeks on FABP4 concentration in patients with type 2 diabetes mellitus at a high risk for cardiovascular events who were receiving statin therapy.

Results

The DPP-4 inhibitor had been administered in 82% of the patients in the anagliptin group and 81% of the patients in sitagliptin group prior to randomization. Serum FABP4 level was significantly decreased by 7.9% by treatment with anagliptin (P = 0.049) and was not significantly decreased by treatment with sitagliptin (P = 0.660). Change in FABP4 level was independently associated with basal FABP4 level and changes in waist circumference and creatinine after adjustment of age, sex and the treatment group.

Conclusion

Anagliptin decreases serum FABP4 concentration independent of change in hemoglobin A1c or LDL-C in patients with type 2 diabetes mellitus and dyslipidemia who are on statin therapy.

Trial registration ClinicalTrials.gov number NCT02330406. Registered January 5, 2015, https://clinicaltrials.gov/ct2/show/NCT02330406

Independent and Distinct Associations of FABP4 and FABP5 With Metabolic Parameters in Type 2 Diabetes Mellitus

Objective: Among fatty acid-binding proteins (FABPs), secreted forms of FABP4 and FABP5, which are expressed in adipocytes and macrophages, act as bioactive molecules. We investigated concentrations of FABP4 and FABP5 in patients with type 2 diabetes mellitus. Methods: As a sub-analysis study of the Randomized Evaluation of Anagliptin vs. Sitagliptin On low-density lipoproteiN cholesterol in diabetes (REASON) trial, 256 patients (male/female: 146/110, age: 68 ± 10 years) with type 2 diabetes mellitus and dyslipidemia who were receiving statin therapy were recruited. Patients who had been treated with a thiazolidinedione were excluded. Results: Several drugs which may modulate FABP4 levels including statins, dipeptidyl peptidase-4 inhibitors and angiotensin II receptor blockers had been administered in 100, 81, and 51% of the recruited patients, respectively. The level of FABP4, but not that of FABP5, was significantly higher in females than in males. Multivariable linear regression analysis demonstrated that waist circumference (β = 0.21), estimated glomerular filtration rate (β = -0.31), triglycerides (β = 0.16), and FABP5 (β = 0.39) were independent predictors of FABP4 level after adjusting age and sex. On the other hand, FABP5 level was independently associated with levels of FABP4 (β = 0.57) and high-density lipoprotein (HDL) cholesterol (β = -0.12). Conclusions: Concentrations of FABP4 and FABP5 are independent predictors of each other in patients with type 2 diabetes mellitus. There are distinct independent associations of FABP4 with renal dysfunction, adiposity and hypertriglyceridemia and there is a distinct independent association of FABP5 with a low HDL cholesterol level in type 2 diabetic patients with dyslipidemia at high risks for cardiovascular disease who are receiving statin therapy.

Fatty Acid-Binding Protein 4 in Cardiovascular and Metabolic Diseases

Fatty acid-binding proteins (FABPs), a family of lipid chaperones, contribute to systemic metabolic regulation via several lipid signaling pathways. Fatty acid-binding protein 4 (FABP4), known as adipocyte FABP (A-FABP) or aP2, is mainly expressed in adipocytes and macrophages and plays important roles in the development of insulin resistance and atherosclerosis in relation to metabolically driven low-grade and chronic inflammation, referred to as ‘metaflammation’. FABP4 is secreted from adipocytes in a non-classical pathway associated with lipolysis and acts as an adipokine for the development of insulin resistance and atherosclerosis. Circulating FABP4 levels are associated with several aspects of metabolic syndrome and cardiovascular disease. Ectopic expression and function of FABP4 in cells and tissues are also related to the pathogenesis of several diseases. Pharmacological modification of FABP4 function by specific inhibitors, neutralizing antibodies or antagonists of unidentified receptors would be novel therapeutic strategies for several diseases, including obesity, diabetes mellitus, atherosclerosis and cardiovascular disease. Significant roles of FABP4 as a lipid chaperone in physiological and pathophysiological conditions and the possibility of FABP4 being a therapeutic target for metabolic and cardiovascular diseases are discussed in this review.

Serum FABP4 concentrations decrease after Roux-en-Y gastric bypass but not after intensive medical management

BACKGROUND

Serum concentrations of fatty acid binding protein 4, an adipose tissue fatty acid chaperone, have been correlated with insulin resistance and cardiovascular risk factors. The objective of this study were to assess relationships among Roux-en-Y gastric bypass, intensive lifestyle modification and medical management protocol, fatty acid binding protein 4, and metabolic parameters in obese patients with severe type 2 diabetes mellitus; and to evaluate the relative contribution of abdominal subcutaneous adipose and visceral adipose to the secretion of fatty acid binding protein 4.

METHODS

Participants were randomly assigned to intensive lifestyle modification and medical management protocol (n = 29) or to intensive lifestyle modification and medical management protocol augmented with Roux-en-Y gastric bypass (n = 34). Relationships among fatty acid binding protein 4 and demographic characteristics, metabolic parameters, and 12-month changes in these values were examined. Visceral and subcutaneous adipose tissue explants from obese nondiabetic patients (n = 5) were obtained and treated with forskolin to evaluate relative secretion of fatty acid binding protein 4 in the different adipose tissue depots.

RESULTS

The intensive lifestyle modification and medical management protocol and Roux-en-Y gastric bypass cohorts had similar fasting serum fatty acid binding protein 4 concentrations at baseline. At 1 year, mean serum fatty acid binding protein 4 decreased by 42% in Roux-en-Y gastric bypass participants (P = .002) but did not change significantly in the intensive lifestyle modification and medical management protocol cohort. Percentage of weight change was not a significant predictor of 12-month fatty acid binding protein 4 within treatment arm or in multivariate models adjusted for treatment arm. In adipose tissue explants, fatty acid binding protein 4 was secreted similarly between visceral and subcutaneous adipose tissue.

CONCLUSION

After Roux-en-Y gastric bypass, fatty acid binding protein 4 is reduced 12 months after surgery but not after intensive lifestyle modification and medical management protocol in patients with type 2 diabetes mellitus. Fatty acid binding protein 4 was secreted similarly between subcutaneous and visceral adipose tissue explants.

Circulating Fatty Acid-Binding Protein 4 Concentration Predicts the Progression of Carotid Atherosclerosis in a General Population Without Medication

BACKGROUND

Fatty acid-binding protein 4 (FABP4), which is expressed in both adipocytes and macrophages, is secreted from the cells and acts as an adipokine. An elevated circulating FABP4 level is associated with insulin resistance and atherosclerosis.Methods and Results:We investigated the causative association between FABP4 level and progression of atherosclerosis in subjects of the Tanno-Sobetsu Study, a population-based cohort. In 281 subjects without medication (male/female: 109/172) in the year 2010 or 2013, the carotid intima-media thickness (CIMT) assessed using carotid ultrasonography was significantly correlated with age, adiposity, blood pressure, renal dysfunction and levels of cholesterol, triglycerides, fasting glucose, HbA1c and FABP4 (r=0.331, P<0.001). Multiple regression analysis demonstrated that age, sex and FABP4 concentration were independent predictors of CIMT. A total of 78 (male/female: 29/49) of the 156 subjects in 2010 underwent carotid ultrasonography again in 2013. The change in CIMT each year during that 3-year period (mean±SD: 3.8±22.3 µm/year) was positively correlated with basal levels of high-sensitivity C-reactive protein (hsCRP) (r=0.231, P=0.046) and FABP4 (r=0.267, P=0.018) in 2010. After adjustment for age, sex and hsCRP level, the basal FABP4 level was independently associated with the change in CIMT per year.

CONCLUSIONS

FABP4 concentration is an independent predictor of the progression of carotid atherosclerosis.

Circulating adipocyte fatty acid-binding protein is a predictor of cardiovascular events in patients with stable angina undergoing percutaneous coronary intervention

Background

Adipocyte fatty acid-binding protein (A-FABP) is expressed in both adipocytes and macrophages. Recent studies have shown that A-FABP is secreted by adipocytes and that the A-FABP concentration is associated with obesity, insulin resistance, and atherosclerosis. We have reported that the coronary atherosclerotic burden is associated with the serum A-FABP concentration. In the present study, we investigated whether the serum A-FABP concentration is associated with prognosis in patients with stable angina pectoris who have undergone percutaneous coronary intervention (PCI).

Methods

This was a prospective single-center trial. In total, 130 patients with stable angina pectoris undergoing their first PCI were enrolled from August 2008 to July 2010 at Kagawa Prefectural Central Hospital. The primary endpoints were cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, revascularization, and hospitalization for heart failure.

Results

During the follow-up (median, 50 months; interquartile range, 23–66 months), 49 cardiovascular events occurred. Kaplan–Meier analysis showed that the cumulative incidence of the primary endpoints in the high A-FABP group (median A-FABP concentration of ≥ 18.6 ng/ml) was greater than that in the low A-FABP group. Cox analysis showed that the A-FABP concentration was an independent predictor of cardiovascular events adjusted for age and the presence of multi-vessel disease (hazard ratio, 1.03; 95% confidence interval, 1.01–1.04; p = 0.01).

Conclusion

The serum A-FABP concentration is associated with prognosis in patients with stable angina undergoing PCI, suggesting that the serum A-FABP concentration could be useful for risk assessment of secondary prevention.

Trial registration

UMIN Clinical Trials Registry UMIN000029283 (registration date: September 25, 2017), retrospectively registered.

Ectopic Fatty Acid-Binding Protein 4 Expression in the Vascular Endothelium is Involved in Neointima Formation After Vascular Injury

Background

Fatty acid‐binding protein 4 (FABP4) is expressed in adipocytes, macrophages, and endothelial cells of capillaries but not arteries. FABP4 is secreted from adipocytes in association with lipolysis, and an elevated circulating FABP4 level is associated with obesity, insulin resistance, and atherosclerosis. However, little is known about the link between FABP4 and endovascular injury. We investigated the involvement of ectopic FABP4 expression in endothelial cells in neointima hyperplasia after vascular injury.

Methods and Results

Femoral arteries of 8‐week‐old male mice were subjected to wire‐induced vascular injury. After 4 weeks, immunofluorescence staining showed that FABP4 was ectopically expressed in endothelial cells of the hyperplastic neointima. Neointima formation determined by intima area and intima to media ratio was significantly decreased in FABP4‐defficient mice compared with that in wild‐type mice. Adenovirus‐mediated overexpression of FABP4 in human coronary artery endothelial cells (HCAECs) in vitro increased inflammatory cytokines and decreased phosphorylation of nitric oxide synthase 3. Furthermore, FABP4 was secreted from HCAECs. Treatment of human coronary smooth muscle cells or HCAECs with the conditioned medium of Fabp4‐overexpressed HCAECs or recombinant FABP4 significantly increased gene expression of inflammatory cytokines and proliferation‐ and adhesion‐related molecules in cells, promoted cell proliferation and migration of human coronary smooth muscle cells, and decreased phosphorylation of nitric oxide synthase 3 in HCAECs, which were attenuated in the presence of an anti‐FABP4 antibody.

Conclusions

Ectopic expression and secretion of FABP4 in vascular endothelial cells contribute to neointima formation after vascular injury. Suppression of ectopic FABP4 in the vascular endothelium would be a novel strategy against post‐angioplasty vascular restenosis.

Serum FABP5 concentration is a potential biomarker for residual risk of atherosclerosis in relation to cholesterol efflux from macrophages

Cholesterol efflux capacity (CEC) from macrophages, the first step in the reverse cholesterol transport pathway, is inversely associated with residual risk for atherosclerotic cardiovascular disease. Fatty acid-binding protein 4 (FABP4) and FABP5 are expressed in both adipocytes and macrophages and play significant roles in the development of insulin resistance and atherosclerosis. Both FABP4 and FABP5 are secreted from cells, and their circulating levels are associated with insulin resistance and atherosclerosis. We investigated the association between CEC and levels of FABP4 and FABP5 in 250 subjects without any medications. CEC was positively correlated with HDL cholesterol level and negatively correlated with concentrations of high-sensitivity C-reactive protein (hsCRP) and FABP5, but not FABP4. Multiple regression analysis demonstrated that FABP5 concentration was an independent predictor of CEC after adjustment of age, gender and levels of HDL cholesterol and hsCRP. In 129 of the 250 subjects who underwent carotid ultrasonography, mean intima-media thickness was negatively correlated with CEC and was positively correlated with concentrations of FABP4 and FABP5. In conclusion, in contrast to FABP4, circulating FABP5 is associated with decreased CEC and carotid atherosclerosis, suggesting that FABP5 level is a regulatory factor of CEC and a potential biomarker for residual risk of atherosclerosis.

Transcriptome and Metabolome Analyses in Exogenous FABP4- and FABP5-Treated Adipose-Derived Stem Cells

Adipose-derived stem cells (ADSC), which exist near adipocytes in adipose tissue, have been used as a potential tool of regenerative medicine. Lipid chaperones, fatty acid-binding protein 4 (FABP4) and 5 (FABP5), are abundantly expressed in adipocytes. FABP4 has recently been shown to be secreted from adipocytes during lipolysis in a non-classical pathway and may act as an adipokine. Here, we investigated the role of exogenous FABP4 and FABP5 in transcriptional and metabolic regulation in ADSC. FABP4 and FABP5 were little expressed in ADSC. However, both FABP4 and FABP5 were significantly induced after adipocyte differentiation of ADSC and were secreted from the differentiated adipocytes. Analysis of microarray data, including gene ontology enrichment analysis and cascade analysis of the protein-protein interaction network using a transcription factor binding site search, demonstrated that treatment of ADSC with FABP4 or FABP5 affected several kinds of genes related to inflammatory and metabolic responses and the process of cell differentiation. Notably, myogenic factors, including myocyte enhancer factors, myogenic differentiation 1 and myogenin, were modulated by treatment of ADSC with FABP4, indicating that exogenous FABP4 treatment is partially associated with myogenesis in ADSC. Metabolome analysis showed that treatment of ADSC with FABP4 and with FABP5 similarly, but differently in extent, promoted hydrolysis and/or uptake of lipids, consequentially together with enhancement of β oxidation, inhibition of downstream of the glycolysis pathway, accumulation of amino acids, reduction of nucleic acid components and increase in the ratio of reduced and oxidized nicotinamide adenine dinucleotide phosphates (NADPH/NADP+), an indicator of reducing power, and the ratio of adenosine triphosphate and adenosine monophosphate (ATP/AMP), an indicator of the energy state, in ADSC. In conclusion, secreted FABP4 and FABP5 from adipocytes as adipokines differentially affect transcriptional and metabolic regulation in ADSC near adipocytes. The adiposity condition in the host of regenerative medicine may affect characteristics of ADSC by exposure of the balance of FABP4 and FABP5.

Adipose-specific inactivation of JNK alleviates atherosclerosis in apoE-deficient mice

Both atherosclerosis and obesity, an independent atherosclerotic risk factor, are associated with enhanced systemic inflammation. Obesity is also characterized by increased adipose tissue inflammation. However, the molecular mechanism underlying the accelerated atherosclerosis in obesity remains unclear. In obesity, activation of c-Jun N-terminal kinase (JNK) contributes to adipose tissue inflammation. The present study investigated whether the suppression of fat inflammation through adipose-specific JNK inactivation could protect against atherosclerosis in mice. ApoE−/− mice were cross-bred with transgenic mice with adipose-specific expression of a dominant negative form of JNK (dnJNK) to generate apoE−/−/dnJNK (ADJ) mice. ADJ mice treated with a high-fat–high-cholesterol diet exhibited significant attenuations of visceral fat and systemic inflammation without changes in lipid or glucose metabolism, and were protected against atherosclerosis, when compared with apoE−/− mice. Lean apoE−/− mice that received transplantation of visceral fat from obese wild-type donor mice for 4 weeks showed exacerbated systemic inflammation and atherosclerotic plaque formation. Conversely, apoE−/− recipients carrying a visceral fat graft from obese dnJNK donors were protected against enhanced systemic inflammation and atherogenesis. The beneficial effects of adipose-specific JNK inactivation on atherogenesis in apoE−/− recipients were significantly compromised by continuous infusion of recombinant adipocyte–fatty acid-binding protein (A-FABP), previously shown to interact with JNK via a positive feedback loop to modulate inflammatory responses. Together these data suggested that enhanced atherosclerosis in obesity can be attributed, at least in part, to a distant cross-talk between visceral fat and the vasculature, mediated by the release of proinflammatory cytokines, such as A-FABP, from the inflamed visceral adipose tissue with JNK activation.

Possible Increase in Serum FABP4 Level Despite Adiposity Reduction by Canagliflozin, an SGLT2 Inhibitor

BACKGROUND

Fatty acid-binding protein 4 (FABP4/A-FABP/aP2) is secreted from adipocytes in association with catecholamine-induced lipolysis, and elevated serum FABP4 level is associated with obesity, insulin resistance and atherosclerosis. Secreted FABP4 as a novel adipokine leads to insulin resistance via increased hepatic glucose production (HGP). Sodium-glucose cotransporter 2 (SGLT2) inhibitors decrease blood glucose level via increased urinary glucose excretion, though HGP is enhanced. Here we investigated whether canagliflozin, an SGLT2 inhibitor, modulates serum FABP4 level.

METHODS

Canagliflozin (100 mg/day) was administered to type 2 diabetic patients (n = 39) for 12 weeks. Serum FABP4 level was measured before and after treatment.

RESULTS

At baseline, serum FABP4 level was correlated with adiposity, renal dysfunction and noradrenaline level. Treatment with canagliflozin significantly decreased adiposity and levels of fasting glucose and HbA1c but increased average serum FABP4 level by 10.3% (18.0 ± 1.0 vs. 19.8 ± 1.2 ng/ml, P = 0.008), though elevation of FABP4 level after treatment was observed in 26 (66.7%) out of 39 patients. Change in FABP4 level was positively correlated with change in levels of fasting glucose (r = 0.329, P = 0.044), HbA1c (r = 0.329, P = 0.044) and noradrenaline (r = 0.329, P = 0.041) but was not significantly correlated with change in adiposity or other variables.

CONCLUSIONS

Canagliflozin paradoxically increases serum FABP4 level in some diabetic patients despite amelioration of glucose metabolism and adiposity reduction, possibly via induction of catecholamine-induced lipolysis in adipocytes. Increased FABP4 level by canagliflozin may undermine the improvement of glucose metabolism and might be a possible mechanism of increased HGP by inhibition of SGLT2.

TRIAL REGISTRATION

UMIN-CTR Clinical Trial UMIN000018151.

Local Production of Fatty Acid-Binding Protein 4 in Epicardial/Perivascular Fat and Macrophages Is Linked to Coronary Atherosclerosis

OBJECTIVE

Fatty acid-binding protein 4 (FABP4) is expressed in adipocytes and macrophages, and elevated circulating FABP4 level is associated with obesity-mediated metabolic phenotype. We systematically investigated roles of FABP4 in the development of coronary artery atherosclerosis.

APPROACH AND RESULTS

First, by immunohistochemical analyses, we found that FABP4 was expressed in macrophages within coronary atherosclerotic plaques and epicardial/perivascular fat in autopsy cases and macrophages within thrombi covering ruptured coronary plaques in thrombectomy samples from patients with acute myocardial infarction. Second, we confirmed that FABP4 was secreted from macrophages and adipocytes cultured in vitro. Third, we investigated the effect of exogenous FABP4 on macrophages and human coronary artery-derived smooth muscle cells and endothelial cells in vitro. Treatment of the cells with recombinant FABP4 significantly increased gene expression of inflammatory markers in a dose-dependent manner. Finally, we measured serum FABP4 level in the aortic root (Ao-FABP4) and coronary sinus (CS-FABP4) of 34 patients with suspected or known coronary artery disease. Coronary stenosis score assessed by the modified Gensini score was weakly correlated with CS-FABP4 but was not correlated with Ao-FABP4. A stronger correlation (r=0.59, P<0.01) was observed for the relationship between coronary stenosis score and coronary veno-arterial difference in FABP4 level, (CS-Ao)-FABP4, indicating local production of FABP4 during coronary circulation in the heart. Multivariate analysis indicated that (CS-Ao)-FABP4 was an independent predictor of the severity of coronary stenosis after adjustment of conventional risk factors.

CONCLUSIONS

FABP4 locally produced by epicardial/perivascular fat and macrophages in vascular plaques contributes to the development of coronary atherosclerosis.

Reduction of circulating FABP4 level by treatment with omega-3 fatty acid ethyl esters

Background

Fatty acid-binding protein 4 (FABP4/A-FABP/aP2) mainly expressed in adipocytes is secreted and acts as an adipokine. Increased circulating FABP4 level is associated with obesity, insulin resistance and atherosclerosis. However, little is known about the modulation of serum FABP4 level by drugs including anti-dyslipidemic agents.

Methods

Patients with dyslipidemia were treated with omega-3 fatty acid ethyl esters (4 g/day; n = 14) containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 4 weeks. Serum FABP4 level was measured before and after treatment. Expression and secretion of FABP4 were also examined in mouse 3T3-L1 adipocytes treated with EPA or DHA.

Results

Treatment with omega-3 fatty acid ethyl esters significantly decreased triglycerides and serum FABP4 level (13.5 ± 1.5 vs. 11.5 ± 1.1 ng/ml, P = 0.017). Change in FABP4 level by omega-3 fatty acids was negatively correlated with change in levels of EPA + DHA (r = −0.643, P = 0.013), EPA (r = −0.540, P = 0.046) and DHA (r = −0.650, P = 0.011) but not change in the level of triglycerides or other fatty acid composition. Treatment of 3T3-L1 adipocytes with EPA or DHA had no effect on short-term (2 h) secretion of FABP4. However, gene expression and long-term (24 h) secretion of FABP4 were significantly reduced by treatment with EPA or DHA.

Conclusions

Omega-3 fatty acids decrease circulating FABP4 level, possibly by reducing expression and consecutive secretion of FABP4 in adipocytes. Reducing FABP4 level might be involved in suppression of cardiovascular events by omega-3 fatty acids.

Reduction of serum FABP4 level by sitagliptin, a DPP-4 inhibitor, in patients with type 2 diabetes mellitus

Fatty acid binding protein 4 (FABP4), also known as adipocyte FABP or aP2, is secreted from adipocytes in association with lipolysis as a novel adipokine, and elevated serum FABP4 level is associated with obesity, insulin resistance, and atherosclerosis. However, little is known about the modulation of serum FABP4 level by therapeutic drugs. Sitagliptin (50 mg/day), a dipeptidyl peptidase 4 (DPP-4) inhibitor that increases glucagon-like peptide 1 (GLP-1), was administered to patients with type 2 diabetes (n = 24) for 12 weeks. Treatment with sitagliptin decreased serum FABP4 concentration by 19.7% (17.8 ± 1.8 vs. 14.3 ± 1.5 ng/ml, P < 0.001) and hemoglobin A1c without significant changes in adiposity or lipid variables. In 3T3-L1 adipocytes, sitagliptin or exendin-4, a GLP-1 receptor agonist, had no effect on short-term (2 h) secretion of FABP4. However, gene expression and long-term (24 h) secretion of FABP4 were significantly reduced by sitagliptin, which was not mimicked by exendin-4. Treatment with recombinant DPP-4 increased gene expression and long-term secretion of FABP4, and the effects were cancelled by sitagliptin. Furthermore, knockdown of DPP-4 in 3T3-L1 adipocytes decreased gene expression and long-term secretion of FABP4. In conclusion, sitagliptin decreases serum FABP4 level, at least in part, via reduction in the expression and consecutive secretion of FABP4 in adipocytes by direct inhibition of DPP-4.

Fatty Acid-Binding Protein 4 (FABP4): Pathophysiological Insights and Potent Clinical Biomarker of Metabolic and Cardiovascular Diseases

Over the past decade, evidences of an integration of metabolic and inflammatory pathways, referred to as metaflammation in several aspects of metabolic syndrome, have been accumulating. Fatty acid-binding protein 4 (FABP4), also known as adipocyte FABP (A-FABP) or aP2, is mainly expressed in adipocytes and macrophages and plays an important role in the development of insulin resistance and atherosclerosis in relation to metaflammation. Despite lack of a typical secretory signal peptide, FABP4 has been shown to be released from adipocytes in a non-classical pathway associated with lipolysis, possibly acting as an adipokine. Elevation of circulating FABP4 levels is associated with obesity, insulin resistance, diabetes mellitus, hypertension, cardiac dysfunction, atherosclerosis, and cardiovascular events. Furthermore, ectopic expression and function of FABP4 in several types of cells and tissues have been recently demonstrated. Here, we discuss both the significant role of FABP4 in pathophysiological insights and its usefulness as a biomarker of metabolic and cardiovascular diseases.

FABP4 is secreted from adipocytes by adenyl cyclase-PKA- and guanylyl cyclase-PKG-dependent lipolytic mechanisms

OBJECTIVE

Fatty acid-binding protein 4 (FABP4) is expressed in adipocytes, and elevated plasma FABP4 level is associated with obesity-mediated metabolic phenotype. Postprandial regulation and secretory signaling of FABP4 has been investigated.

METHODS

Time courses of FABP4 levels were examined during an oral glucose tolerance test (OGTT; n=53) or a high-fat test meal eating (n=35). Effects of activators and inhibitors of adenyl cyclase (AC)-protein kinase A (PKA) signaling and guanylyl cyclase (GC)-protein kinase G (PKG) signaling on FABP4 secretion from mouse 3T3-L1 adipocytes were investigated.

RESULTS

FABP4 level significantly declined after the OGTT or a high-fat meal eating, while insulin level was increased. Treatment with low and high glucose concentration or palmitate for 2 h did not affect FABP4 secretion from 3T3-L1 adipocytes. FABP4 secretion was increased by stimulation of lipolysis using isoproterenol, a β3 -adrenoceptor agonist (CL316243), forskolin, dibutyryl-cAMP and atrial natriuretic peptide, and the induced FABP4 secretion was suppressed by insulin or an inhibitor of PKA (H-89), PKG (KT5823) or hormone sensitive lipase (CAY10499).

CONCLUSIONS

FABP4 is secreted from adipocytes in association with lipolysis regulated by AC-PKA- and GC-PKG-mediated signal pathways. Plasma FABP4 level declines postprandially, and suppression of FABP4 secretion by insulin-induced anti-lipolytic signaling may be involved in this decline in FABP4 level.

Urinary excretion of fatty acid-binding protein 4 is associated with albuminuria and renal dysfunction

Background

Fatty acid-binding protein 4 (FABP4/A-FABP/aP2) is expressed in not only adipocytes and macrophages but also peritubular capillaries in the normal kidney. We recently demonstrated that ectopic expression of FABP4, but not FABP1 known as liver FABP (L-FABP), in the glomerulus is associated with progression of proteinuria and renal dysfunction. However, urinary excretion of FABP4 has not been investigated.

Methods

Subjects who participated in the Tanno-Sobetsu Study, a study with a population-based cohort design, in 2011 (n = 392, male/female: 166/226) were enrolled. Urinary FABP4 (U-FABP4) and urinary albumin-to-creatinine ratio (UACR) were measured. Change in estimated glomerular filtration rate (eGFR) was followed up one year later.

Results

In 93 (23.7%) of the 392 subjects, U-FABP4 level was below the sensitivity of the assay. Subjects with undetectable U-FABP4 were younger and had lower UACR and higher eGFR levels than subjects with measurable U-FABP4. U-FABP4 level was positively correlated with age, systolic blood pressure and levels of serum FABP4 (S-FABP4), triglycerides, hemoglobin A1c (HbA1c), urinary FABP1 (U-FABP1) and UACR (r = 0.360, p<0.001). Age, S-FABP4, U-FABP1 and UACR were independent predictors of U-FABP4. On the other hand, systolic blood pressure, HbA1c and U-FABP4 were independently correlated with UACR. Reduction in eGFR after one year was significantly larger in a group with the highest tertile of baseline U-FABP4 than a group with the lowest tertile.

Conclusions

Urinary FABP4 level is independently correlated with level of albuminuria and possibly predicts yearly decline of eGFR. U-FABP4 would be a novel biomarker of glomerular damage.

Mechanism and clinical evidence of lipocalin-2 and adipocyte fatty acid-binding protein linking obesity and atherosclerosis

Obesity is considered to be a chronic inflammatory state in which the dysfunction of adipose tissue plays a central role. The adipokines, which are cytokines secreted by adipose tissue, are key links between obesity and related diseases such as metabolic syndrome and atherosclerosis. LCN2 and A-FABP, both of which are major adipokines predominantly produced in adipose tissue, have recently been shown to be pivotal modulators of vascular function. However, different adipokines modulate the development of atherosclerosis in distinctive manners, which are partly attributable to their unique regulatory mechanisms and functions. This review highlights recent advances in the understanding of the role of two adipokines in mediating chronic inflammation and the pathogenesis of atherosclerosis.

Elevation of circulating fatty acid-binding protein 4 is independently associated with left ventricular diastolic dysfunction in a general population

Background

Fatty acid-binding protein 4 (FABP4) is expressed in both adipocytes and macrophages. Recent studies have shown secretion of FABP4 from adipocytes and association of elevated serum FABP4 level with obesity, insulin resistance, hypertension, and atherosclerosis. However, little is known about role of FABP4 in cardiac function.

Methods

From the database of the Tanno-Sobetsu Study, data for 190 subjects (male/female: 82/108) who were not treated with any medication and underwent echocardiography in 2011 or 2012 were retrieved for analyses of relationships between serum FABP4 concentration, metabolic markers and parameters of echocardiography.

Results

Serum FABP4 level was positively correlated with age, body mass index (BMI), blood pressure (BP), LDL cholesterol, HOMA-R and mean left ventricular (LV) wall thickness (LVWT, males: r = 0.315, females: r = 0.401, p < 0.01) and was negatively correlated with HDL cholesterol, estimated glomerular filtration rate (eGFR) and peak myocardial velocity during early diastole (e’; males: r = −0.434, females: r = −0.353, p < 0.01), an index of LV diastolic function. However, no significant correlation was found between FABP4 level and LV end-diastolic dimension, LV ejection fraction or LV mass index. There were significant correlations of e’ with age, BMI, BP, eGFR, brain natriuretic peptide (BNP), FABP4, metabolic markers and LVWT. Multivariate regression analysis adjusted by HOMA-R, BMI, eGFR, BNP or LVWT in addition to age, gender and BP revealed that serum FABP4 concentration was independently correlated with e’.

Conclusions

Elevation of circulating FABP4 may contribute to LV diastolic dysfunction in a general population.

Pilot study of A-FABP levels as a predictive factor of SPECT results in asymptomatic relatives of patients with cardiovascular disease

BACKGROUND

A-FABP is a promising link between metabolic syndrome and atherosclerosis. It is not well known whether level of A-FABP predicts results of SPECT.

PATIENTS & METHODS

In 82 subjects (53 males) with a median age of 54 years, who were first-degree relatives of patients with cardiovascular disease, the following tests and examinations were performed: A-FABP, calcium score (CS) and SPECT.

RESULTS

Subjects with positive and negative SPECT results differed significantly in the noncategorized CS (p = 0.001), uric acid (p = 0.025) and the total cholesterol:high-density lipoprotein ratio (p = 0.043), but not in other parameters (including A-FABP). To predict SPECT results, the best model proved to be a logistic regression model with gender and noncategorized CS as predictors, with an area under the receiver operating characteristic curve of 0.89 (the sensitivity and specificity based on a CS cutoff of 11.1 were 77.78 and 75.34%, respectively).

CONCLUSION

The serum level of A-FABP is not a predictor of a positive SPECT result.

Intervention for cardiovascular risk factors decreases adipocyte fatty acid-binding protein levels in males — a pilot study

Cardiovascular disease (CVD) remains the leading cause of mortality in developed countries. According to the 2012 European Guidelines on Cardiovascular Disease Prevention in Clinical Practice, family history is a cornerstone for risk stratification of CVD. First-degree relatives are persons in whom CVD should be assessed and targeted intervention should be performed. The aims of this pilot study were (i) to determine risk factors (RFs) for cardiovascular disease (CVD) in a group of first-degree relatives of patients with CVD at baseline and after 1 year, (ii) to measure adipocyte fatty acid-binding protein (A-FABP) levels as a potential connecting link between metabolic disease and atherosclerosis, and (iii) to determine the impact of targeted intervention on these parameters. The study comprised 62 asymptomatic subjects (41 males; mean age of 53.8±8.3 years). Preventive examinations and interventions were carried out at baseline and at 1-year follow-up to assess RFs and evaluate A-FABP levels. At 1 year, males had significantly lower levels of cholesterol (median 5.18 vs 4.67, p=0.005), HDL (median 1.24 vs 1.14, p=0.021), LDL (median 3.08 vs 2.46, p=0.021), ApoB (median 0.99 vs 0.82, p=0.012) and A-FABP (median 19.84 vs 16.73, p = 0.015). In females after 1 year, only significantly lower levels of fibrinogen (median 3.10 vs 2.79, p=0.043) were found. All subjects were clinically examined or contacted by phone after a mean of 36.7 months (range, 11–55). Over that time, no serious complications were noted. In males, intervention for RFs leads to lower levels of A-FABP as a potential RF linking metabolic syndrome to atherosclerosis.

Lipid chaperones and metabolic inflammation

Over the past decade, a large body of evidence has emerged demonstrating an integration of metabolic and immune response pathways. It is now clear that obesity and associated disorders such as insulin resistance and type 2 diabetes are associated with a metabolically driven, low-grade, chronic inflammatory state, referred to as “metaflammation.” Several inflammatory cytokines as well as lipids and metabolic stress pathways can activate metaflammation, which targets metabolically critical organs and tissues including adipocytes and macrophages to adversely affect systemic homeostasis. On the other hand, inside the cell, fatty acid-binding proteins (FABPs), a family of lipid chaperones, as well as endoplasmic reticulum (ER) stress, and reactive oxygen species derived from mitochondria play significant roles in promotion of metabolically triggered inflammation. Here, we discuss the molecular and cellular basis of the roles of FABPs, especially FABP4 and FABP5, in metaflammation and related diseases including obesity, diabetes, and atherosclerosis.

Association of increased plasma adipocyte fatty acid-binding protein with coronary artery disease in non-elderly men

Background

Adipocyte fatty acid-binding protein (A-FABP) has been reported to play critical roles in the development of atherosclerosis. We investigated whether an increased in plasma A-FABP level can be independently associated with the presence of coronary artery disease (CAD).

Methods

Two hundred eleven consecutive male patients (mean age: 66 years, range: 33-87 years) were enrolled from inpatients who underwent coronary angiography. Age-matched male subjects (n = 211) having no evidence of CAD served as controls. Plasma A-FABP levels were measured by enzyme-linked immunosorbent assays.

Results

Plasma A-FABP levels in CAD patients were significantly higher than in control subjects (median [IQR], 20.6 [15.7-27.8] ng/mL vs. 15.1 [11.7-19.9] ng/mL, p < 0.01). Multivariate logistic regression analysis revealed that an increased plasma A-FABP level was independently associated with the presence of CAD in all subjects (adjusted odds ratio: 1.76, 95% confidence interval: 1.14 to 2.70, p = 0.01). Furthermore, sub-analysis based on age showed that this association remained significant in subjects aged < 65 years (adjusted odds ratio: 3.06, 95% confidence interval: 1.34 to 6.98, p < 0.01), but not in subjects aged ≥65 years.

Conclusions

Increased plasma A-FABP in non-elderly men had a significant association with the presence of CAD, independent of established CAD risk factors.

Randomized head-to-head comparison of pitavastatin, atorvastatin, and rosuvastatin for safety and efficacy (quantity and quality of LDL): the PATROL trial

BACKGROUND

Atorvastatin, rosuvastatin and pitavastatin are available for intensive, aggressive low-density lipoprotein cholesterol (LDL-C)-lowering therapy in clinical practice. The objective of the Randomized Head-to-Head Comparison of Pitavastatin, Atorvastatin, and Rosuvastatin for Safety and Efficacy (Quantity and Quality of LDL) (PATROL) Trial was to compare the safety and efficacy of atorvastatin, rosuvastatin and pitavastatin head to head in patients with hypercholesterolemia. This is the first prospective randomized multi-center trial to compare these strong statins (UMIN Registration No: 000000586).

METHODS AND RESULTS

Patients with risk factors for coronary artery disease and elevated LDL-C levels were randomized to receive atorvastatin (10mg/day), rosuvastatin (2.5mg/day), or pitavastatin (2mg/day) for 16 weeks. Safety was assessed in terms of adverse event rates, including abnormal clinical laboratory variables related to liver and kidney function and skeletal muscle. Efficacy was assessed by the changes in the levels and patterns of lipoproteins. Three hundred and two patients (from 51 centers) were enrolled, and these 3 strong statins equally reduced LDL-C and LDL particles, as well as fast-migrating LDL (modified LDL) by 40-45%. Newly developed pitavastatin was non-inferior to the other 2 statins in lowering LDL-C. There were no differences in the rate of adverse drug reactions among the 3 groups, but HbA(1c) was increased while uric acid was decreased in the atorvastatin and rosuvastatin groups.

CONCLUSIONS

The safety and efficacy of these 3 strong statins are equal. It is suggested that the use of these 3 statins be completely dependent on physician discretion based on patient background.

Fasting serum fatty acid-binding protein 4 level positively correlates with metabolic syndrome in hemodialysis patients

BACKGROUND AND AIMS

Serum fatty acid-binding protein 4 (FABP4) level increases in patients with metabolic syndrome (MetS). The interrelationships between fasting FABP4 levels and MetS have not been analyzed in hemodialysis (HD) patients.

METHODS

Fasting blood samples were obtained from 101 chronic HD patients. MetS was defined according to the diagnostic criteria of the International Diabetes Federation.

RESULTS

In total, 48 HD patients (47.5%) had MetS. Fasting FABP4 levels positively correlated with MetS (p = 0.022). Univariate linear regression analysis showed that the pre-HD body weight (p <0.001), waist circumference (p = 0.003), body mass index (p = 0.003), total cholesterol (TCH) (p <0.001), triglyceride (TG) (p <0.001), creatinine (p = 0.042), insulin level (p = 0.014), and homeostasis model assessment of insulin resistance (HOMA-IR; p = 0.015) were positively correlated with serum FABP4 levels, whereas high-density lipoprotein-cholesterol (HDL-C) (p = 0.049) and adiponectin level (p = 0.004) were negatively correlated with fasting serum FABP4 levels in HD patients.

CONCLUSIONS

MetS was positively correlated with fasting FABP4 levels in our chronic HD patients. TG, TCH, and waist circumference were independent predictors of serum FABP4 levels in HD patients.

Different association of circulating levels of adipocyte and epidermal fatty acid-binding proteins with metabolic syndrome and coronary atherosclerosis in Chinese adults

AIMS

Adipocyte and epidermal fatty acid-binding protein (A-FABP, E-FABP) are cytoplasmic proteins which may play an important role in metabolic diseases. In the present study, we investigated the different association of A-FABP and E-FABP with metabolic syndrome (MetS) and coronary artery disease (CAD) in Chinese adults.

METHODS

A total of 459 subjects (233 MetS and 226 non-MetS) who had undergone coronary angiography were enrolled in the present study. Serum A-FABP and E-FABP levels, glucose, lipid profiles and other biochemical markers were measured.

RESULTS

Both serum A-FABP and E-FABP levels were significantly higher in the MetS group than in the non-MetS group (P = 0.040 and 0.045, respectively). Only serum A-FABP levels in the CAD group were significantly higher than in the non-CAD group (12.30 ± 5.45 vs.10.94 ± 4.94 ng/mL, P= 0.008), and significantly increased with the increasing of number of disease vessels (P=0.004). Serum A-FABP levels were also associated with risk of CAD (odds ratio 2.956 [1.295-6.748]; P = 0.010). Adjusting for age, sex, and other conventional risk factors for CAD did not appreciably change the results. No difference was found in serum E-FABP levels between CAD status. Serum E-FABP levels were correlated with fasting and post load 2h plasma glucose, HbA1c, serum total cholesterol and LDL-C concentrations while serum A-FABP levels were correlated with fasting and post load 2h serum insulin concentrations and HOMA-IR (different P<0.05).

CONCLUSIONS

Our data indicated while both serum A-FABP and E-FABP levels had associations with MetS, only A-FABP was significantly associated with increased risk of CAD in Chinese adults.

Fasting serum level of fatty-acid-binding protein 4 positively correlates with metabolic syndrome in patients with coronary artery disease

BACKGROUND

The serum level of fatty-acid-binding protein 4 (FABP4) increases in patients with metabolic syndrome (MetS), so the relationship between FABP4 and MetS among patients with coronary artery disease (CAD) was investigated in the present study.

METHODS AND RESULTS

Fasting blood samples were obtained from 98 CAD patients. MetS and its components were defined using the diagnostic criteria of the International Diabetes Federation; 50 CAD patients (51.0%) had MetS. The fasting level of FABP4 positively correlated with MetS (P=0.037) and serum levels of FABP4 correlated with a number of MetS criteria (P=0.035). Univariate linear regression analysis showed that body fat mass (R=0.234; P=0.020) and the levels of triglycerides (R=0.348; P<0.001), and low-density lipoprotein-cholesterol (R=0.217; P=0.032) positively correlated with the serum level of FABP4, whereas the level of high-density lipoprotein-cholesterol (R=-0.243; P=0.016) negatively correlated with it. Multivariate forward stepwise linear regression analysis of the significant variables showed that the level of triglycerides (beta=0.348, R(2)=0.121, P<0.001) was the independent predictor of fasting serum level of FABP4.

CONCLUSIONS

Among CAD patients in the present study, the fasting level of FABP4 positively correlated with MetS and serum levels of FABP4 correlated with a number of MetS criteria.

Serum fatty acid binding protein 4, free fatty acids, and metabolic risk markers

Fatty acid binding protein (FABP) 4 chaperones free fatty acids (FFAs) in the adipocytes during lipolysis. Serum FFA relates to metabolic syndrome, and serum FABP4 is emerging as a novel risk marker. In 36 overweight/obese women, serum FABP4 and FFA were measured hourly during 5-hour oral glucose tolerance test. Insulin resistance was determined using frequently sampled intravenous glucose tolerance test. Serum lipids and inflammation markers were measured at fasting. During oral glucose tolerance test, serum FABP4 decreased by 40%, reaching its nadir at 3 hours (from 45.3 +/- 3.1 to 31.9 +/- 1.6 ng/mL), and stayed below the baseline at 5 hours (35.9 +/- 2.2 ng/mL) (P < .0001 for both, compared with the baseline). Serum FFA decreased by 10-fold, reaching a nadir at 2 hours (from 0.611 +/- 0.033 to 0.067 +/- 0.004 mmol/L), then rebounded to 0.816 +/- 0.035 mmol/L at 5 hours (P < .001 for both, compared with baseline). Both fasting FABP4 and nadir FABP4 correlated with obesity. Nadir FABP4 correlated also with insulin resistance parameters from frequently sampled intravenous glucose tolerance test and with inflammation. Nadir FFA, but not fasting FFA, correlated with the metabolic syndrome parameters. In conclusion, fasting FABP4 related to metabolic risk markers more strongly than fasting FFA. Nadir FABP4 and nadir FFA measured after glucose loading may provide better risk assessment than the fasting values.

Simvastatin increases osteoblasts and osteogenic proteins in ovariectomized rats

BACKGROUND

Previous reports have indicated that statins could prevent bone loss in ovariectomized (OVX) rats and increase the expressions of osteogenic genes in cultured osteoblasts. In this study, we hypothesized that simvastatin might increase osteoblast number and protein expressions of osteogenic markers localized in bones in concomitance with the prevention of bone loss in OVX rats.

MATERIALS AND METHODS

Fifty-four 3-month-old OVX and sham-operated (SHAM) female Sprague-Dawley rats were used. Simvastatin (10-20 mg kg(-1) day(-1)) was administrated orally for 6 weeks. Trabecular volume, osteoblast number and osteogenic proteins including BMP2, collagen type I and osteocalcin on bone sections obtained from lumbar vertebral body, distal femur and proximal tibia were measured.

RESULTS

The results showed that SHAM rats had significantly less trabecular bone volume and osteoblast number than that of OVX rats 6 weeks after operation. Oral simvastatin treatment (10-20 mg kg(-1) day(-1)) increased bone volume and osteoblast number in the distal femurs, proximal tibiae and vertebrae of OVX rats. Furthermore, the osteoblastic cells with immuno-stained BMP2, collagen type I and osteocalcin in vertebral bones were significantly increased by simvastatin treatment (20 mg kg(-1) day(-1)) in OVX rats.

CONCLUSIONS

This study demonstrates that simvastatin enhances the production of osteogenic proteins in bone and this effect may contribute to the prevention of bone loss in OVX rats.

Fatty acid binding proteins in adipose tissue: a promising link between metabolic syndrome and atherosclerosis?

Adipocyte/macrophage fatty acid binding protein (A-FABP) has been shown to be closely associated with metabolic syndrome, obesity and development of atherosclerosis. Moreover, A-FABP has been recently suggested as a potential therapeutic target of these abnormalities in animal models. The present review aims to summarize current knowledge on A-FABP functions and regulations both in animal models and humans, since the role of A-FABP in human physiology and disease has not been presently clarified.