Adipocyte fatty acid-binding protein levels are associated with left ventricular diastolic dysfunction in morbidly obese subjects

Metabolic syndrome, left ventricular diastolic dysfunction and heart failure with preserved ejective fraction

Metabolic syndrome (MetS) encompasses a cluster of interrelated conditions, including obesity, hyperglycemia, hyperlipidemia, and hypertension, and has been established as a significant risk factor for cardiovascular events and heightened mortality. At its core, insulin resistance serves as the primary underlying mechanism driving the development of MetS. The prevalence of MetS is rising at an alarming rate, posing a significant public health challenge worldwide. Even in the absence of overt obstructive coronary artery disease or valvular heart disease, patients with MetS often exhibit adverse cardiac remodeling and myocardial dysfunction. Left ventricular hypertrophy (LVH) and left ventricular diastolic dysfunction (LVDD) are the leading manifestations of heart failure with preserved ejection fraction (HFpEF). Abnormal myocardial substrate utilization, neurohormonal activation, interstitial fibrosis, coronary microvascular dysfunction, and metabolic inflammation have all been implicated in the development and progression of adverse cardiac remodeling associated with MetS. However, despite the tremendous research produced on this subject, HFpEF remains highly prevalent in such a population. The early diagnosis of abnormal cardiac remodeling would enable optimal effective therapies to prevent the progression of the disease to the symptomatic phase. HFpEF encompasses a diverse range of pathological processes. In these patients, LVDD and elevated left ventricular filling pressure are the primary manifestations. Echocardiography remains the popular imaging modality for the assessment of LVDD and LV filling pressure. The article aims to review recent articles covering the association between MetS components or MetS and LVDD in HFpEF.

Up-regulated fatty acid-binding protein 4 promoted cardiac injury during open colorectal surgery in elderly patients

BACKGROUND

Fatty acid binding protein 4 (FABP4) has been shown to increase cardiovascular disease. The FABP4 levels in serum and adipose tissue and the possible regulatory mechanisms during colorectal cancer surgery in elderly patients remain unknown.

METHODS

Four hundred elderly patients with colorectal cancer were recruited, 200 underwent laparoscopic surgery (LS) and 200 underwent open surgery (OS). Blood samples and mesenteric adipose tissue were collected at T1 (beginning of surgery) and T2 (end of surgery). Immunohistochemistry and biochemical analysis were used to evaluate the FABP4, cardiac troponin T (cTnT), creatine kinase-MB (CK-MB) and myoglobin (MYO) levels. Correlations between FABP4 and cTnT, CK-MB, MYO were further analyzed.

RESULTS

The expressions of FABP4 in mesenteric adipose tissue were significantly increased at T2 than T1 in OS group. The serum levels of FABP4, cTnT, CK-MB and MYO were significantly increased at T2 than T1 in OS group, and the OS group induced higher FABP4, cTnT, CK-MB and MYO levels than LS group at T2. Pearson's correlation analysis revealed that serum levels of FABP4 were strongly correlated with cTnT, CK-MB, and MYO.

CONCLUSIONS

OS induced significantly increased FABP4 expressions in adipose tissue and caused cardiac injury in elderly patients with colorectal cancer. FABP4 is closely associated with cardiac injury, raising the possibility that adipose tissue may be causally involved in the pathogenesis of heart dysfunction during open surgery.

Fatty Acid Binding Proteins 3 and 4 Predict Both All-Cause and Cardiovascular Mortality in Subjects with Chronic Heart Failure and Type 2 Diabetes Mellitus

Subjects with type 2 diabetes mellitus (T2D) are at increased risk for heart failure (HF). The cardiac-specific (FABP3) and adipose-tissue-specific (FABP4) types of the fatty acid binding proteins have been associated with both all-cause and cardiovascular (CV) mortality. The aim of this study was to explore the prognosis value of FABP3 and FABP4 in ambulatory subjects with chronic HF (CHF), with and without T2D. A prospective study involving 240 ambulatory CHF subjects was performed. Patients were followed-up for a mean of 5.78 ± 3.30 years and cause of death (if any) was recorded. Primary endpoints were defined as all-cause and CV death, and a composite endpoint that included CV death or hospitalization for HF was included as a secondary endpoint. Baseline serum samples were obtained and the serum FABP3 and FABP4 concentrations were assessed by sandwich enzyme-linked immunosorbent assay. Survival analysis was performed with multivariable Cox regressions, using Fine and Gray competing risks models when needed, to explore the prognostic value of FABP3 and FABP4 concentrations, adjusting for potential confounders. Type 2 diabetes mellitus was highly prevalent, accounting for 47.5% for total subjects with CHF. Subjects with T2D showed higher mortality rates (T2D: 69.30%; non-T2D: 50.79%, p = 0.004) and higher serum FABP3 (1829.3 (1104.9–3440.5) pg/mL vs. 1396.05 (820.3–2362.16) pg/mL, p = 0.007) and FABP4 (45.5 (27.6–79.8) ng/mL vs. 34.1 (24.09–55.3) ng/mL, p = 0.006) concentrations compared with non-T2D CHF subjects. In the whole study cohort, FABP3 was independently associated with all-cause death, and both FABP3 and FABP4 concentrations were associated with CV mortality. The predictive values of these two molecules for all-cause (FABP3: HR 1.25, 95% CI 1.09–1.44; p = 0.002. FABP4: HR 2.21, 95% CI 1.12–4.36; p = 0.023) and CV mortality (FABP3: HR 1.28, 95% CI 1.09–1.50; p = 0.002. FABP4: HR 4.19, 95% CI 2.21–7.95; p < 0.001) were only statistically significant in the subgroup of subjects with T2D. Notably, FABP4 (HR 2.07, 95% CI 1.11–3.87; p = 0.022), but not FABP3, also predicted the occurrence of the composite endpoint (death or hospitalization for HF) only in subjects with T2D. All these associations were not found in CHF subjects without T2D. Our findings support the usefulness of serum FABP3 and FABP4 concentrations as independent predictors for the occurrence of all-cause and CV mortality in ambulatory subjects with CHF with T2D.

Blood and Urinary Biomarkers of Antipsychotic-Induced Metabolic Syndrome

Metabolic syndrome (MetS) is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Antipsychotic (AP)-induced MetS (AIMetS) is the most common adverse drug reaction (ADR) of psychiatric pharmacotherapy. Herein, we review the results of studies of blood (serum and plasma) and urinary biomarkers as predictors of AIMetS in patients with schizophrenia (Sch). We reviewed 1440 studies examining 38 blood and 19 urinary metabolic biomarkers, including urinary indicators involved in the development of AIMetS. Among the results, only positive associations were revealed. However, at present, it should be recognized that there is no consensus on the role of any particular urinary biomarker of AIMetS. Evaluation of urinary biomarkers of the development of MetS and AIMetS, as one of the most common concomitant pathological conditions in the treatment of patients with psychiatric disorders, may provide a key to the development of strategies for personalized prevention and treatment of the condition, which is considered a complication of AP therapy for Sch in clinical practice.

Lipids and diastolic dysfunction: Recent evidence and findings

AIM

Diastolic dysfunction is the decreased flexibility of the left ventricle due to the impaired ability of the myocardium to relax and plays an important role in the pathogenesis of heart failure. Lipid metabolism is a well-known contributor to cardiac conditions, including ventricular function. In this article, we aimed to review the literature addressing the connections between lipids, their storage, and metabolism with left ventricular diastolic dysfunction.

DATA SYNTHESIS

We searched Google scholar, Pubmed, Embase and Researchgate for our keywords: "Diastolic function", "Fat" and "Lipid profile". Initially, 250 articles were selected by title and 84 of them were chosen as most relevant and directly reviewed.

CONCLUSIONS

Alterations of lipid metabolism in cardiac muscle and cardiac lipid content can occur in many conditions, including consumption of a high-fat diet, obesity, metabolic syndrome, and non-alcoholic fatty liver disease (NAFLD). These conditions induce alterations in myocardial lipid metabolism, increase myocardial fat content and epicardial fat thickness and increase inflammation and oxidative stress which ultimately lead to cardiac lipotoxicity and diastolic dysfunction. The effects of lipids on diastolic function can differ based on gender. Lipid profile and metabolism are as important in the pathogenesis of diastolic dysfunction as they are in other cardiovascular disorders. A more careful look at cardiac lipid metabolism in molecular, histological and gross levels results in more precise understanding of its role in myocardial function and leads to development of potential treatments for diastolic dysfunction.

Machine Learning-Derived Echocardiographic Phenotypes Predict Heart Failure Incidence in Asymptomatic Individuals

OBJECTIVES

This study sought to identify homogenous echocardiographic phenotypes in community-based cohorts and assess their association with outcomes.

BACKGROUND

Asymptomatic cardiac dysfunction leads to a high risk of long-term cardiovascular morbidity and mortality; however, better echocardiographic classification of asymptomatic individuals remains a challenge.

METHODS

Echocardiographic phenotypes were identified using K-means clustering in the first generation of the STANISLAS (Yearly non-invasive follow-up of Health status of Lorraine insured inhabitants) cohort (N = 827; mean age: 60 ± 5 years; men: 48%), and their associations with vascular function and circulating biomarkers were also assessed. These phenotypes were externally validated in the Malmö Preventive Project cohort (N = 1,394; mean age: 67 ± 6 years; men: 70%), and their associations with the composite of cardiovascular mortality (CVM) or heart failure hospitalization (HFH) were assessed as well.

RESULTS

Three echocardiographic phenotypes were identified as "mostly normal (MN)" (n = 334), "diastolic changes (D)" (n = 323), and "diastolic changes with structural remodeling (D/S)" (n = 170). The D and D/S phenotypes had similar ages, body mass indices, cardiovascular risk factors, vascular impairments, and diastolic function changes. The D phenotype consisted mainly of women and featured increased levels of inflammatory biomarkers, whereas the D/S phenotype, consisted predominantly of men, displayed the highest values of left ventricular mass, volume, and remodeling biomarkers. The phenotypes were predicted based on a simple algorithm including e', left ventricular mass and volume (e'VM algorithm). In the Malmö cohort, subgroups derived from e'VM algorithm were significantly associated with a higher risk of CVM and HFH (adjusted HR in the D phenotype = 1.87; 95% CI: 1.04 to 3.37; adjusted HR in the D/S phenotype = 3.02; 95% CI: 1.71 to 5.34).

CONCLUSIONS

Among asymptomatic, middle-aged individuals, echocardiographic data-driven classification based on the simple e'VM algorithm identified profiles with different long-term HF risk. (4th Visit at 17 Years of Cohort STANISLAS-Stanislas Ancillary Study ESCIF [STANISLASV4]; NCT01391442).

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.

Prospective association of serum adipocyte fatty acid-binding protein with heart failure hospitalization in diabetes

AIMS

Adipocyte fatty acid-binding protein (AFABP) is associated with cardiovascular diseases in type 2 diabetes. Whether circulating AFABP levels are associated with the risk of heart failure (HF) in type 2 diabetes remains undefined. We investigated the prospective association of circulating AFABP levels with incident HF hospitalization in type 2 diabetes, and its relationship to the use of sodium glucose co-transporter 2 inhibitors (SGLT2i) which reduce HF risk.

METHODS AND RESULTS

Baseline serum AFABP level was measured in 3322 Chinese participants without known history of cardiovascular diseases or hospitalization for HF, recruited from the Hong Kong West Diabetes Registry. Its association with incident HF hospitalization was evaluated using multivariable Cox regression analysis. Use of SGLT2i was included as a time-dependent covariate. Among these 3322 participants (52.9% men; mean age 60.0 ± 12.6), 176 (5.3%) developed HF hospitalization over a median follow-up of 8 years. Seven hundred and thirty-one (22%) were started on SGLT2i during the study period (empagliflozin 55.1%, dapagliflozin 44.2%, canagliflozin 0.4%, and ertugliflozin 0.3%). Serum AFABP levels were significantly higher in participants who developed HF hospitalization than those who did not (men: 14.8 vs. 8.3 ng/mL; women: 21.5 vs. 14.6 ng/mL; all: 18.6 vs. 10.9 ng/mL, P < 0.001). In multivariable Cox regression analysis, baseline serum AFABP level was significantly associated with incident HF hospitalization [hazard ratio (HR) 1.38, 95% confidence interval (CI) 1.06-1.80, P = 0.019] independent of the use of SGLT2i, in a model also consisting of age; sex; body mass index; smoking status; duration of diabetes; hypertension, dyslipidaemia; atrial fibrillation; presence of chronic kidney disease and albuminuria; glycated haemoglobin and high-sensitivity C-reactive protein levels; and use of metformin, insulin, aspirin, furosemide, and beta-blockers at baseline. High cumulative defined daily dose (cDDD) of SGLT2i was protective of incident HF hospitalization (HR 0.10, 95% CI 0.01-0.68, P = 0.019). The addition of circulating AFABP level to a clinical model of conventional HF risk factors provided significant improvement in the category-free net reclassification index (11.5%, 95% CI 1.6-22.1, P = 0.02) and integrated discrimination improvement (0.3%, 95% CI 0.1-1.7, P = 0.04). A dose-dependent reduction in cumulative incidence of HF hospitalization in response to SGLT2i, based on cDDD, was more clearly observed in participants with a higher baseline AFABP level above the sex-specific median (P for trend <0.01).

CONCLUSIONS

Circulating AFABP level is independently associated with incident HF hospitalization in type 2 diabetes and is potentially helpful in risk stratification for the prevention of HF hospitalization.

Elevated S-adenosylhomocysteine induces adipocyte dysfunction to promote alcohol-associated liver steatosis

It has been previously shown that chronic ethanol administration-induced increase in adipose tissue lipolysis and reduction in the secretion of protective adipokines collectively contribute to alcohol-associated liver disease (ALD) pathogenesis. Further studies have revealed that increased adipose S-adenosylhomocysteine (SAH) levels generate methylation defects that promote lipolysis. Here, we hypothesized that increased intracellular SAH alone causes additional related pathological changes in adipose tissue as seen with alcohol administration. To test this, we used 3-deazaadenosine (DZA), which selectively elevates intracellular SAH levels by blocking its hydrolysis. Fully differentiated 3T3-L1 adipocytes were treated in vitro for 48 h with DZA and analysed for lipolysis, adipokine release and differentiation status. DZA treatment enhanced adipocyte lipolysis, as judged by lower levels of intracellular triglycerides, reduced lipid droplet sizes and higher levels of glycerol and free fatty acids released into the culture medium. These findings coincided with activation of both adipose triglyceride lipase and hormone sensitive lipase. DZA treatment also significantly reduced adipocyte differentiation factors, impaired adiponectin and leptin secretion but increased release of pro-inflammatory cytokines, IL-6, TNF and MCP-1. Together, our results demonstrate that elevation of intracellular SAH alone by DZA treatment of 3T3-L1 adipocytes induces lipolysis and dysregulates adipokine secretion. Selective elevation of intracellular SAH by DZA treatment mimics ethanol's effects and induces adipose dysfunction. We conclude that alcohol-induced elevations in adipose SAH levels contribute to the pathogenesis and progression of ALD.

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.

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.

Pathophysiological role of fatty acid-binding protein 4 in Asian patients with heart failure and preserved ejection fraction

Aims

Systemic metabolic impairment is the key pathophysiology of heart failure (HF) with preserved ejection fraction (HFpEF). Fatty acid‐binding protein 4 (FABP4) is highly expressed in adipocytes and secreted in response to lipolytic signals. We hypothesized that circulating FABP4 levels would be elevated in patients with HFpEF, would correlate with cardiac structural and functional abnormalities, and could predict clinical outcomes.

Methods and results

Serum FABP4 measurements and echocardiography were performed in patients with HFpEF (n = 92) and those with coronary artery disease free of HF (n = 20). Patients were prospectively followed‐up for a composite endpoint of all‐cause mortality or HF hospitalization. Compared with patients with coronary artery disease, those with HFpEF had higher FABP4 levels [12.5 (9.1–21.0) vs. 43.5 (24.6–77.4) ng/mL, P < 0.0001]. FABP4 levels were associated with cardiac remodelling (left ventricular mass index: r = 0.29, P = 0.002; left atrial volume index: r = 0.40, P < 0.0001), left ventricular systolic and diastolic dysfunction (global longitudinal strain: r = −0.24, P = 0.01; E/e′ ratio: r = 0.29, P = 0.002; and N‐terminal pro‐B‐type natriuretic peptide: r = 0.62, P < 0.0001), and right ventricular dysfunction (tricuspid annular plane systolic excursion: r = −0.43, P < 0.0001). During a median follow‐up of 9.1 months, there were 28 primary endpoints in the HFpEF cohort. Event‐free survival was significantly decreased in patients with FABP4 levels ≥43.5 ng/mL than in those with FABP4 levels <43.5 ng/mL (P = 0.003).

Conclusions

Serum FABP4 levels were increased in HFpEF and were associated with cardiac remodelling and dysfunction, and poor outcomes. Thus, FABP4 could be a potential biomarker in the complex pathophysiology of HFpEF.

The adipokine fatty-acid binding protein 4 and cardiac remodeling

BACKGROUND

Previous publications about the association between fatty-acid binding protein 4 (FABP4) and cardiac remodeling have reported different, both beneficial and harmful, associations. Aim of the present investigation was to evaluate the association of FABP4 with parameters of myocardial remodeling defined by cardiac magnetic resonance imaging (CMR).

METHODS

We investigated plasma FABP4 levels in 331 patients (71% men, mean age 63±13 years) with preserved left ventricular ejection fraction (LVEF ≥ 55%) who underwent a CMR examination. We used linear cox regression to investigate associations between FABP4 and left ventricular end-diastolic diameter (LVEDD), right ventricular end-diastolic diameter (RVEDD), relative wall thickness (RWT), left ventricular mass index (LVMI), and LVEF (unadjusted and adjusted for age, sex, body mass index, cardiac biomarkers, and comorbidities).

RESULTS

FABP4 levels were associated with lower LVMI and higher NT-proBNP levels in an adjusted model. The inverse association between FABP4 and LVMI was more pronounced in lower FABP4 levels, whereas the positive association between FABP4 and NT-proBNP was more pronounced in relatively high NT-proBNP levels.

CONCLUSIONS

Possible beneficial and harmful associations between FABP4 and left ventricular size have been reported. Our results suggest a beneficial association with LVMI (more pronounced in lower FABP4 levels) but a harmful association with NT-proBNP (more pronounced in higher FABP4 levels). Therefore, our results might indicate a potential dose-dependent association of FABP4, but this observation needs further investigation in larger study samples.

Barth Syndrome: Exploring Cardiac Metabolism with Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Barth syndrome (BTHS) is an X-linked recessive multisystem disorder caused by mutations in the TAZ gene (TAZ, G 4.5, OMIM 300394) that encodes for the acyltransferase tafazzin. This protein is highly expressed in the heart and plays a significant role in cardiolipin biosynthesis. Heart disease is the major clinical manifestation of BTHS with a high incidence in early life. Although the genetic basis of BTHS and tetralinoleoyl cardiolipin deficiency in BTHS-affected individuals are well-established, downstream metabolic changes in cardiac metabolism are still uncovered. Our study aimed to characterize TAZ-induced metabolic perturbations in the heart. Control (PGP1-TAZWT) and TAZ mutant (PGP1-TAZ517delG) iPS-CM were incubated with 13C6-glucose and 13C5-glutamine and incorporation of 13C into downstream Krebs cycle intermediates was traced. Our data reveal that TAZ517delG induces accumulation of cellular long chain acylcarnitines and overexpression of fatty acid binding protein (FABP4). We also demonstrate that TAZ517delG induces metabolic alterations in pathways related to energy production as reflected by high glucose uptake, an increase in glycolytic lactate production and a decrease in palmitate uptake. Moreover, despite mitochondrial dysfunction, in the absence of glucose and fatty acids, TAZ517delG-iPS-CM can use glutamine as a carbon source to replenish the Krebs cycle.

Landscape of heart proteome changes in a diet-induced obesity model

Obesity is a pandemic associated with a high incidence of cardiovascular disease; however, the mechanisms are not fully elucidated. Proteomics may provide a more in-depth understanding of the pathophysiological mechanisms and contribute to the identification of potential therapeutic targets. Thus, our study evaluated myocardial protein expression in healthy and obese rats, employing two proteomic approaches. Male Wistar rats were established in two groups (n = 13/group): control diet and Western diet fed for 41 weeks. Obesity was determined by the adipose index, and cardiac function was evaluated in vivo by echocardiogram and in vitro by isolated papillary muscle analysis. Proteomics was based on two-dimensional gel electrophoresis (2-DE) along with mass spectrometry identification, and shotgun proteomics with label-free quantification. The Western diet was efficient in triggering obesity and impaired contractile function in vitro; however, no cardiac dysfunction was observed in vivo. The combination of two proteomic approaches was able to increase the cardiac proteomic map and to identify 82 differentially expressed proteins involved in different biological processes, mainly metabolism. Furthermore, the data also indicated a cardiac alteration in fatty acids transport, antioxidant defence, cytoskeleton, and proteasome complex, which have not previously been associated with obesity. Thus, we define a robust alteration in the myocardial proteome of diet-induced obese rats, even before functional impairment could be detected in vivo by echocardiogram.

Dedifferentiation of mature adipocytes with periodic exposure to cold

 Lipid-containing adipocytes can dedifferentiate into fibroblast-like cells under appropriate culture conditions, which are known as dedifferentiated fat (DFAT) cells. However, the relative low dedifferentiation efficiency with the established protocols limit their widespread applications. In this study, we found that adipocyte dedifferentiation could be promoted via periodic exposure to cold (10°C) in vitro. The lipid droplets in mature adipocytes were reduced by culturing the cells in periodic cooling/heating cycles (10-37°C) for one week. The periodic temperature change led to the down-regulation of the adipogenic genes (FABP4, Leptin) and up-regulation of the mitochondrial uncoupling related genes (UCP1, PGC-1α, and PRDM16). In addition, the enhanced expression of the cell proliferation marker Ki67 was observed in the dedifferentiated fibroblast-like cells after periodic exposure to cold, as compared to the cells cultured in 37°C. Our in vitro model provides a simple and effective approach to promote lipolysis and can be used to improve the dedifferentiation efficiency of adipocytes towards multipotent DFAT cells.

Fatty acid binding protein 4 (FABP4) as a potential biomarker reflecting myocardial lipid storage in type 2 diabetes

OBJECTIVE

Fatty acid binding protein 4 (FABP4) is an intracellular lipid chaperone involved in the crosstalk between adipose and peripheral tissues, and it contributes to widespread insulin resistance in cells, including cardiac cells. However, the role of this adipokine in regulating cardiac metabolism and myocardial neutral lipid content in patients with type 2 diabetes has not been elucidated.

METHODS

The impact of circulating FABP4 on the cardiac neutral lipid content was measured by proton magnetic resonance spectroscopy (¹H-MRS) in patients with type 2 diabetes. Additionally, circulating FABP4 and the cardiac triglyceride content were analysed in high-fat diet (HFD)-fed mice, and the impact of the exogenous FABP4 was explored in HL-1 cardiac cells.

RESULTS

Serum FABP4 levels were higher in type 2 diabetic patients compared to healthy individuals. Circulating FABP4 levels were associated with myocardial neutral lipid content in type 2 diabetic patients. In HFD-fed mice, both serum FABP4 and myocardial triglyceride content were increased. In FABP4-challenged HL-1 cells, extracellular FABP4 increased intracellular lipid accumulation, which led to impairment of the insulin-signalling pathway and reduced insulin-stimulated glucose uptake. However, these effects were partially reversed by FABP4 inhibition with BMS309403, which attenuated the intracellular lipid content and improved insulin signalling and insulin-stimulated glucose uptake.

CONCLUSIONS

Taken together, our results identify FABP4 as a molecule involved in diabetic/lipid-induced cardiomyopathy and indicate that this molecule may be an emerging biomarker for diabetic cardiomyopathy-related disturbances, such as myocardial neutral lipid accumulation. Additionally, FABP4 inhibition may be a potential therapeutic target for metabolic-related cardiac dysfunctions.

Association of serum adipocyte fatty acid-binding protein and apolipoprotein B /apolipoprotein A1 ratio with intima media thickness of common carotid artery in dyslipidemic patients

BACKGROUND

Diseases caused by atherosclerosis play the most important role in mortality and morbidity worldwide. Serum adipocyte fatty acid binding protein (A-FABP) seems to be a new promising marker to determine the risk of atherosclerosis.

OBJECTIVE

The aim of this study was to evaluate relationships between serum A-FABP levels in studied individuals and to assess the possibility of modeling the intima media thickness of the common carotid artery (C-IMT) using A-FABP levels and other observed characteristics.

METHODS

Seventy two Caucasian individuals were enrolled and divided into 3 groups: dyslipidemic patients with or without metabolic syndrome (MetS+, n=17; MetS-, n= 34) and controls (n=21).

RESULTS

There was confirmed the well-established risk profile of individuals with MetS (unfavorable lipid and lipoprotein profile, as well as increased parameters of insulin resistence and C-IMT). A-FABP concentrations in this group were significantly higher in comparison with both MetS- and controls.

CONCLUSION

Using multiple linear regression models of C-IMT values for all individual data, healthy controls and dyslipidemic patients without metabolic syndrome (MetS-) A-FABP levels were not revealed as an important predictor of C-IMT in our model. In contrast, age, gender, waist circumference, nonHDL cholesterol levels and ApoB/ApoA1 ratio were important repressors of C- IMT in study individuals. This finding may be attributed to the overwhelming effect of other more robust risk factors for atherosclerosis in these individuals.

Association of Circulating Adipokines With Echocardiographic Measures of Cardiac Structure and Function in a Community-Based Cohort

BACKGROUND

Adipokines mediate cardiometabolic risk associated with obesity but their role in the pathogenesis of obesity-associated heart failure remains uncertain. We investigated the associations between circulating adipokine concentrations and echocardiographic measures in a community-based sample.

METHODS AND RESULTS

We evaluated 3514 Framingham Heart Study participants (mean age 40 years, 53.8% women) who underwent routine echocardiography and had select circulating adipokines measured, ie, leptin, soluble leptin receptor, fatty acid-binding protein 4, retinol-binding protein 4, fetuin-A, and adiponectin. We used multivariable linear regression, adjusting for known correlates (including weight), to relate adipokine concentrations (independent variables) to the following echocardiographic measures (dependent variables): left ventricular mass index, left atrial diameter in end systole, fractional shortening, and E/e'. In multivariable-adjusted analysis, left ventricular mass index was inversely related to circulating leptin and fatty acid-binding protein 4 concentrations but positively related to retinol-binding protein 4 and leptin receptor levels (P≤0.002 for all). Left atrial end-systolic dimension was inversely related to leptin but positively related to retinol-binding protein 4 concentrations (P≤0.0001). E/e' was inversely related to leptin receptor levels (P=0.0002). We observed effect modification by body weight for select associations (leptin receptor and fatty acid-binding protein 4 with left ventricular mass index, and leptin with left atrial diameter in end systole; P<0.05 for interactions). Fractional shortening was not associated with any of the adipokines. No echocardiographic trait was associated with fetuin-A or adiponectin concentrations.

CONCLUSIONS

In our cross-sectional study of a large, young to middle-aged, relatively healthy community-based sample, key indices of subclinical cardiac remodeling were associated with higher or lower circulating concentrations of prohypertrophic and antihypertrophic adipokines in a context-specific manner. These observations may offer insights into the pathogenesis of the cardiomyopathy of obesity.

Investigating interactions between epicardial adipose tissue and cardiac myocytes: what can we learn from different approaches?

Heart disease is a major cause of morbidity and mortality throughout the world. Some cardiovascular conditions can be modulated by lifestyle factors such as increased exercise or a healthier diet, but many require surgical or pharmacological interventions for their management. More targeted and less invasive therapies would be beneficial. Recently, it has become apparent that epicardial adipose tissue plays an important role in normal and pathological cardiac function, and it is now the focus of considerable research. Epicardial adipose tissue can be studied by imaging of various kinds, and these approaches have yielded much useful information. However, at a molecular level, it is more difficult to study as it is relatively scarce in animal models and, for practical and ethical reasons, not always available in sufficient quantities from patients. What is needed is a robust model system in which the interactions between epicardial adipocytes and cardiac myocytes can be studied, and physiologically relevant manipulations performed. There are drawbacks to conventional culture methods, not least the difficulty of culturing both cardiac myocytes and adipocytes, each of which has special requirements. We discuss the benefits of a three-dimensional co-culture model in which in vivo interactions can be replicated.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Role of the fatty acid-binding protein 4 in heart failure and cardiovascular disease

Obesity and ectopic fat accumulation in non-adipose tissues are major contributors to heart failure (HF) and cardiovascular disease (CVD). Adipocytes act as endocrine organs by releasing a large number of bioactive molecules into the bloodstream, which participate in a communication network between white adipose tissue and other organs, including the heart. Among these molecules, fatty acid-binding protein 4 (FABP4) has recently been shown to increase cardiometabolic risk. Both clinical and experimental evidence have identified FABP4 as a relevant player in atherosclerosis and coronary artery disease, and it has been directly related to cardiac alterations such as left ventricular hypertrophy (LVH) and both systolic and diastolic cardiac dysfunction. The available interventional studies preclude the establishment of a direct causal role of this molecule in CVD and HF and propose FABP4 as a biomarker rather than as an aetiological factor. However, several experimental reports have suggested that FABP4 may act as a direct contributor to cardiac metabolism and physiopathology, and the pharmacological targeting of FABP4 may restore some of the metabolic alterations that are conducive to CVD and HF. Here, we review the current knowledge regarding FABP4 in the context of HF and CVD as well as the molecular basis by which this protein participates in the regulation of cardiac function.

Possitive correlation between adipocyte fatty acid-binding protein and epicardial fat in patients with a family history of cardiovascular disesase

BACKGROUND

Adipocyte fatty acid-binding protein (A-FABP) is a promising link between metabolic syndrome and atherosclerosis. Epicardial fat (EPI) is an independent risk factor for cardiovascular disease (CVD).

OBJECTIVE

The aim of this pilot study was to evaluate the correlation between EPI and A-FABP in asymptomatic patients with a family history of CVD.

METHODS

59 subjects (39 males) (median = 54 years old) were enrolled in the study and their EPI thickness and A-FABP levels were assessed.

RESULTS

EPI was found in 46 patients (77.9%). There were positive correlations between EPI and A-FABP (r=0.336; P=0.010), age (r=0.526; P<0.001), fibrinogen (r=0.304; P=0.023) and systolic blood pressure (r=0.279; P=0.034). A positive correlation was found between EPI and A-FABP in a subgroup of overweight and obese patients (0.389; P=0.041, 0.407; P=0.004) and in the subgroup of patients with excluded CVD (r=0.368; P=0.006).

CONCLUSIONS

We found a positive correlation between EPI and A-FABP in a group of patients with a family history of CVD and in subgroups of overweight and obese patients.

Plasma fatty acid-binding protein 4 (FABP4) as a novel biomarker to predict gestational diabetes mellitus

AIMS

Fatty acid-binding protein 4 (FABP4) is mainly expressed in adipocytes and macrophages and is demonstrated to be elevated in diabetes patients. The aim of this study was to evaluate the possible role of FABP4 in the diagnosis of GDM and to investigate the relationship between FABP4 and overweight, insulin resistance and inflammatory marker TNF-α.

METHODS

A total of 46 women with GDM and 55 age-matched pregnant women without GDM (non-GDM) were eligible for the study. Demographic and biochemical parameters and fasting venous blood samples of two groups were collected from all cases. Serum concentrations of FABP4 were determined using enzyme-linked immunosorbent assay (ELISA). The predictive value of Serum FABP4 level was evaluated using receiver operating characteristic curve (ROC curve) analysis.

RESULTS

We found that the serum FABP4 levels were significantly higher in GDM compared to the non-GDM group. The area under the ROC curve assay yielded a satisfactory result of 0.94 (95 % confidence interval 0.90-0.98; p < 0.001). The best compromise between 86.96 % specificity and 89.09 % sensitivity was obtained with a cutoff value of 1.96 ng/mL for GDM diagnosis. Moreover, a significant positive correlation was observed between FABP4 and overweight, insulin resistance and TNF-α in pregnant women with GDM.

CONCLUSIONS

These results suggest that serum FABP4 may potentially serve as a novel biomarker for the prediction of GDM.

Serum Fatty Acid Binding Protein 4 Concentrations Are Positively and Independently Associated with Blood Pressure and Abdominal Fat among Parameters in Health Check-Ups in Ordinary Middle-Aged Japanese Males

We wished to examine potential associations among blood concentrations of fatty acid-binding protein (FABP) 4 and parameters in health check-ups such as abdominal fat area (AFA) and blood pressure (BP) in middle-aged Japanese males. We conducted a cross-sectional study of males who participated in health check-ups in Japan. We excluded participants diagnosed with metabolic diseases by the time of their check-up. A total of 305 subjects (30-64 [mean±standard deviation, 47.3±8.5] y) were recruited. Areas of total-abdominal, visceral and subcutaneous fat were measured using computed tomography. We compared the association of serum concentrations of FABP4 with various clinical parameters by Pearson product-moment correlation coefficient (PPMCC) analyses, and by step-wise multivariate linear regression analyses (MLRA). PPMCC analyses showed that blood concentrations of FABP4 were positively associated with: body mass index; areas of fat (total abdominal, visceral, subcutaneous); systolic BP; diastolic BP; total cholesterol; low-density lipoprotein-cholesterol; triacylglycerol; activities of γ-glutamyl transpeptidase, aspartate aminotransferase and alanine aminotransferase; white blood cell count; and levels of creatinine. Step-wise MLRA showed that AFAs (visceral and subcutaneous) and diastolic BP were positively and independently associated with serum concentrations of FABP4 among the parameters tested. These data suggest that serum concentrations of FABP4 are independently and positively associated with BP and AFA among parameters measured in health check-ups in middle-aged Japanese males.

Cardiomyocyte Overexpression of FABP4 Aggravates Pressure Overload-Induced Heart Hypertrophy

Fatty acid binding protein 4 (FABP4) is a member of the intracellular lipid-binding protein family, responsible for the transportation of fatty acids. It is considered to express mainly in adipose tissues, and be strongly associated with inflammation, obesity, diabetes and cardiovasculardiseases. Here we report that FABP4 is also expressed in cardiomyocytes and plays an important role in regulating heart function under pressure overload. We generated heart-specific transgenic FABP4 (FABP4-TG) mice using α myosin-heavy chain (α-MHC) promoter and human FABP4 sequence, resulting in over-expression of FABP4 in cardiomyocytes. The FABP4-TG mice displayed normal cardiac morphology and contractile function. When they were subjected to the transverse aorta constriction (TAC) procedure, the FABP4-TG mice developed more cardiac hypertrophy correlated with significantly increased ERK phosphorylation, compared with wild type controls. FABP4 over-expression in cardiomyocytes activated phosphor-ERK signal and up-regulate the expression of cardiac hypertrophic marker genes. Conversely, FABP4 induced phosphor-ERK signal and hypertrophic gene expressions can be markedly inhibited by an ERK inhibitor PD098059 as well as the FABP4 inhibitor BMS309403. These results suggest that FABP4 over-expression in cardiomyocytes can aggravate the development of cardiac hypertrophy through the activation of ERK signal pathway.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

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

Fatty acid binding proteins 4 and 5 in overweight prepubertal boys: effect of nutritional counselling and supplementation with an encapsulated fruit and vegetable juice concentrate

Elevated fatty acid binding proteins (FABP) may play a role in obesity and co-morbidities. The role of nutritional interventions in modulating these levels remains unclear. The aim of this post hoc study was to determine the effect of overweight (OW) on FABP4 and FABP5 in boys in relation to indices of adiposity, insulin resistance and inflammation, and to investigate the effects of a 6-month supplementation with an encapsulated fruit and vegetable juice concentrate (FVJC) plus nutritional counselling (NC) on FABP levels. A post hoc analysis of a double-blind, randomised, placebo-controlled study of children recruited from the general paediatric population was performed. A total of thirty age-matched prepubertal boys (nine lean and twenty-one OW; aged 6-10 years) were studied. Patients received NC by a registered dietitian and were randomised to FVJC or placebo capsules for 6 months. FABP4, FABP5, glucose, insulin, homeostasis model assessment-insulin resistance (HOMA-IR), glucose-induced acute insulin response (AIR), lipid-corrected β-carotene (LCβC), adiponectin, leptin, high-sensitivity C-reactive protein (hs-CRP), IL-6 and body composition by dual-energy X-ray absorptiometry were determined before and after the intervention. FABP were higher (P < 0·01) in the OW v. lean boys and correlated directly with HOMA-IR, abdominal fat mass (AFM), hs-CRP, IL-6, and LCβC (P < 0·05 for all). FABP4 was associated with adiponectin and AIR (P < 0·05). FVJC plus NC reduced FABP4, HOMA-IR and AFM (P < 0·05 for all) but not FABP5. OW boys showed elevated FABP4 and FABP5, but only FABP4 was lowered by the FVJC supplement.

Association Between Serum Levels of Adipocyte Fatty Acid-binding Protein and Free Thyroxine

Adipocyte fatty acid-binding protein (AFABP) has been shown to be a biomarker of body weight change and atherosclerosis. Changes in thyroid function are associated with changes in body weight and risks of cardiovascular diseases. The association between AFABP and thyroid function status has been seldom evaluated.The aim of this study was to compare the serum AFABP concentrations in hyperthyroid patients and those in euthyroid individuals, and to evaluate the associations between serum AFABP and free thyroxine (fT4) levels.For this study, 30 hyperthyroid patients and 30 euthyroid individuals at a referral medical center were recruited. The patients with hyperthyroidism were treated with antithyroid regimens as clinically indicated. No medication was given to the euthyroid individuals. The body weight, body mass index, thyroid function, serum levels of AFABP, and biochemical data of both groups at baseline and at the 6th month were compared. Associations between AFABP and fT4 levels were also analyzed.At the baseline, the hyperthyroid patients had significantly higher serum AFABP levels than the euthyroid individuals (median [Q1, Q3]: 22.8 [19.4, 30.6] ng/mL vs 18.6 [15.3, 23.2] ng/mL; P = 0.038). With the antithyroid regimens, the AFABP serum levels of the hyperthyroid patients decreased to 16.6 (15.0, 23.9) ng/mL at the 6th month. No difference in the AFABP level was found between the hyperthyroid and the euthyroid groups at the 6th month. At baseline, sex (female vs male, ß = 7.65, P = 0.022) and fT4 level (ß = 2.51, P = 0.018) were significantly associated with AFABP levels in the univariate regression analysis. At the 6th month, sex and fT4 level (ß = 8.09, P < 0.001 and ß = 3.61, P = 0.005, respectively) were also significantly associated with AFABP levels. The associations between sex and fT4 level with AFABP levels remained significant in the stepwise multivariate regression analysis, both at baseline and at the 6th month.The patients with hyperthyroidism had higher serum AFABP levels than the individuals with euthyroidism. In the patients with hyperthyroidism, the serum AFABP concentrations decreased after the antithyroid treatment. In this study, the serum AFABP concentrations were positively associated with female sex and the serum fT4 level.

Deficiency of adipocyte fatty-acid-binding protein alleviates myocardial ischaemia/reperfusion injury and diabetes-induced cardiac dysfunction

Clinical evidence shows that circulating levels of adipocyte fatty-acid-binding protein (A-FABP) are elevated in patients with diabetes and closely associated with ischaemic heart disease. Patients with diabetes are more susceptible to myocardial ischaemia/reperfusion (MI/R) injury. The experiments in the present study investigated the role of A-FABP in MI/R injury with or without diabetes. Non-diabetic and diabetic (streptozotocin-induced) A-FABP knockout and wild-type mice were subjected to MI/R or sham intervention. After MI/R, A-FABP knockout mice exhibited reductions in myocardial infarct size, apoptotic index, oxidative and nitrative stress, and inflammation. These reductions were accompanied by an improved left ventricular function compared with the relative controls under non-diabetic or diabetic conditions. After diabetes induction, A-FABP knockout mice exhibited a preserved cardiac function compared with that in wild-type mice. Endothelial cells, but not cardiomyocytes, were identified as the most likely source of cardiac A-FABP. Cardiac and circulating A-FABP levels were significantly increased in mice with diabetes or MI/R. Diabetes-induced superoxide anion production was significantly elevated in wild-type mice, but diminished in A-FABP knockout mice, and this elevation contributed to the exaggeration of MI/R-induced cardiac injury. Phosphorylation of endothelial nitric oxide synthase (eNOS) and production of nitric oxide (NO) were enhanced in both diabetic and non-diabetic A-FABP knockout mice after MI/R injury, but diminished in wild-type mice. The beneficial effects of A-FABP deficiency on MI/R injury were abolished by the NOS inhibitor NG-nitro-L-arginine methyl ester. Thus, A-FABP deficiency protects mice against MI/R-induced and/or diabetes-induced cardiac injury at least partially through activation of the eNOS/NO pathway and reduction in superoxide anion production.

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.

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.