Adipocyte fatty acid binding protein: a novel adipokine involved in the pathogenesis of metabolic and vascular disease?

Unraveling the rationale and conducting a comprehensive assessment of KD025 (Belumosudil) as a candidate drug for inhibiting adipogenic differentiation-a systematic review

Rho-associated kinases (ROCKs) are crucial during the adipocyte differentiation process. KD025 (Belumosudil) is a newly developed inhibitor that selectively targets ROCK2. It has exhibited consistent efficacy in impeding adipogenesis across a spectrum of in vitro models of adipogenic differentiation. Given the novelty of this treatment, a comprehensive systematic review has not been conducted yet. This systematic review aims to fill this knowledge void by providing readers with an extensive examination of the rationale behind KD025 and its impacts on adipogenesis. Preclinical evidence was gathered owing to the absence of clinical trials. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and the study's quality was assessed using the Joanna Briggs Institute (JBI) Checklist Critical Appraisal Tool for Systematic Reviews. In various in vitro models, such as 3T3-L1 cells, human orbital fibroblasts, and human adipose-derived stem cells, KD025 demonstrated potent anti-adipogenic actions. At a molecular level, KD025 had significant effects, including decreasing fibronectin (Fn) expression, inhibiting ROCK2 and CK2 activity, suppressing lipid droplet formation, and reducing the expression of proadipogenic genes peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα). Additionally, KD025 resulted in the suppression of fatty acid-binding protein 4 (FABP4 or AP2) expression, a decrease in sterol regulatory element binding protein 1c (SREBP-1c) and Glut-4 expression. Emphasis must be placed on the fact that while KD025 shows potential in preclinical studies and experimental models, extensive research is crucial to assess its efficacy, safety, and potential therapeutic applications thoroughly and directly in human subjects.

A Prediction Model for Sight-Threatening Diabetic Retinopathy Based on Plasma Adipokines among Patients with Mild Diabetic Retinopathy

Background

Accumulating evidence has suggested a link between adipokines and diabetic retinopathy (DR). This study is aimed at investigating the risk factors for sight-threatening DR (STDR) and establishing a prognostic model for predicting STDR among a high-risk population of patients with type 2 diabetes mellitus (T2DM).

Methods

Plasma concentrations of adipokines were determined by enzyme-linked immunosorbent assay. In the case-control set, principal component analysis (PCA) was performed to select optimal predictive cytokines for STDR, involving severe nonproliferative DR (NPDR) and proliferative DR. Support vector machine (SVM) was used to examine the possible combination of baseline plasma adipokines to discriminate the patients with mild NPDR who will later develop STDR. An individual prospective cohort with a follow-up period of 3 years was used for the external validation.

Results

In both training and testing sets, involving 306 patients with T2DM, median levels of plasma adiponectin (APN), leptin, and fatty acid-binding protein 4 (FABP4) were significantly higher in the STDR group than those in mild NPDR. Except for adipsin, the other three adipokines, FABP4, APN, and leptin, were selected by PCA and integrated into SVM. The accuracy of the multivariate SVM classification model was acceptable in both the training set (AUC = 0.81, sensitivity = 71%, and specificity = 91%) and the testing set (AUC = 0.77, sensitivity = 61%, and specificity = 92%). 110 T2DM patients with mild NPDR, the high-risk population of STDR, were enrolled for external validation. Based on the SVM, the risk of each patient was calculated. More STDR occurred in the high-risk group than in the low-risk group, which were grouped by the median value of APN, FABP4, and leptin, respectively. The model was validated in an individual cohort using SVM with the AUC, sensitivity, and specificity reaching 0.77, 64%, and 91%, respectively.

Conclusions

Adiponectin, leptin, and FABP4 were demonstrated to be associated with the severity of DR and maybe good predictors for STDR, suggesting that adipokines may play an important role in the pathophysiology of DR development.

NRF2 Deficiency Attenuates Diabetic Kidney Disease in Db/Db Mice via Down-Regulation of Angiotensinogen, SGLT2, CD36, and FABP4 Expression and Lipid Accumulation in Renal Proximal Tubular Cells

The role(s) of nuclear factor erythroid 2-related factor 2 (NRF2) in diabetic kidney disease (DKD) is/are controversial. We hypothesized that Nrf2 deficiency in type 2 diabetes (T2D) db/db mice (db/dbNrf2 knockout (KO)) attenuates DKD progression through the down-regulation of angiotensinogen (AGT), sodium-glucose cotransporter-2 (SGLT2), scavenger receptor CD36, and fatty -acid-binding protein 4 (FABP4), and lipid accumulation in renal proximal tubular cells (RPTCs). Db/dbNrf2 KO mice were studied at 16 weeks of age. Human RPTCs (HK2) with NRF2 KO via CRISPR-Cas9 genome editing and kidneys from patients with or without T2D were examined. Compared with db/db mice, db/dbNrf2 KO mice had lower systolic blood pressure, fasting blood glucose, kidney hypertrophy, glomerular filtration rate, urinary albumin/creatinine ratio, tubular lipid droplet accumulation, and decreased expression of AGT, SGLT2, CD36, and FABP4 in RPTCs. Male and female mice had similar results. NRF2 KO attenuated the stimulatory effect of the Nrf2 activator, oltipraz, on AGT, SGLT2, and CD36 expression and high-glucose/free fatty acid (FFA)-stimulated lipid accumulation in HK2. Kidneys from T2D patients exhibited markedly higher levels of CD36 and FABP4 in RPTCs than kidneys from non-diabetic patients. These data suggest that NRF2 exacerbates DKD through the stimulation of AGT, SGLT2, CD36, and FABP4 expression and lipid accumulation in RPTCs of T2D.

Elevated Serum Concentration of Adipocyte Fatty Acid-Binding Protein Correlates with the Markers of Abdominal Obesity Independently of Thyroid Hormones in Non-Obese Women with Polycystic Ovary Syndrome

Adipocyte fatty acid-binding protein (A-FABP) is mainly expressed in adipocytes. The risk of abdominal obesity and autoimmune thyroid disease is increased in women with polycystic ovary syndrome (PCOS). The objective of this study was to explore the relationship of serum concentration of A-FABP with parameters of obesity, e.g., waist to hip ratio (WHR) and the amount of adipose tissue assessed by bioelectrical impedance analysis (BIA), and thyroid hormone homeostasis in women with PCOS. We examined 66 women with PCOS and 67 healthy women. Serum concentrations of A-FABP and thyroid hormones were measured; the FT3/FT4 ratio, thyroid-stimulating hormone index (TSHI), thyrotrope thyroxine resistance index (TT4RI) and thyroid feedback quantile-based index (TFQI) were calculated. In the PCOS group, serum concentrations of A-FABP, FT3 and the FT3/FT4 ratio were significantly higher in comparison to the control group (all p < 0.05). A correlation of A-FABP with WHR (r = 0.26, p = 0.04) and the percentage of adipose tissue (r = 0.33, p = 0.01) has been found only in women with PCOS. We observed no correlation between serum levels of A-FABP and TSHI, TT4RI or TFQI in women with PCOS (all p > 0.05). Our results indicate that A-FABP is an adipokine that may be connected with abdominal obesity independently of thyroid hormone homeostasis in PCOS patients.

A Notorious Trio! Inflammation, Metabolic Syndrome and Vitiligo

Background

There is evidence to support that vitiligo is linked to metabolic syndrome (MS), confirming its systemic nature. However, the underlying pathogenic mechanisms remain unknown.

Objectives

To reveal the possible association of MS with vitiligo. We also attempted to study the connection between some inflammatory markers and MS in vitiligo patients to evaluate their utility in predicting MS risk.

Materials and Methods

The study included 100 vitiligo patients with an age range between 18 to 60 years and 100 controls with matched age, gender, and body mass index. All subjects were tested for MS components. Serum visceral adipose tissue-derived serine protease inhibitor (vaspin), fatty acid binding protein 4 (FABP4), vascular adhesion protein 1 (VAP-1), chitinase-3-like protein 1 (YKL-40), and high-sensitivity C-reactive protein (hs-CRP) were also measured.

Results

Regarding MS, it was observed in 22.0% of vitiligo patients and 2.0% of control subjects (P < 0.001). Serum FABP4, VAP-1, YKL-40, and hs-CRP concentrations were higher in patients than in the control group (P < 0.05 each), and their levels showed high sensitivity and specificity to differentiate MS when using the receiver operating characteristic (ROC). Levels of these markers, except serum vaspin, were significantly positively correlated with lipid profile markers (except high-density lipoprotein cholesterol) and fasting blood glucose levels (P < 0.05 each).

Conclusion

MS was more common in vitiligo patients. The levels of the biomarkers studied were significantly higher in vitiligo patients. Furthermore, their levels accurately predicted MS in vitiligo patients. According to current research, these markers may be useful in assessing MS risk in vitiligo patients. Extensive research, however, is required.

Adipokines in Pregnancy: A Systematic Review of Clinical Data

Adipokines are signaling proteins involved in metabolic, endocrinological, vascular and immunogenic processes. Associations of various adipokines with not only insulin resistance but also with increased insulin sensitivity, increased systolic blood pressure, and atherosclerosis highlight the significance of adipokines in several components of metabolic syndrome and metabolic diseases in general. As pregnancy presents a unique metabolic state, the role of adipokines in pregnancy, and even in various pregnancy complications, appears to be key to elucidating these metabolic processes. Many studies in recent years have attempted to clarify the role of adipokines in pregnancy and gestational pathologies. In this review, we aim to investigate the changes in maternal adipokine levels in physiological gestation, as well as the association of adipokines with pregnancy pathologies, such as gestational diabetes mellitus (GDM) and preeclampsia (PE). Furthermore, we will analyze the association of adipokines in both maternal serum and cord blood with parameters of intrauterine growth and various pregnancy outcomes.

Optimization of potent, selective and orally bioavailable biphenyl scaffold as FABP4 inhibitors for anti-inflammation

Fatty-acid binding protein 4 (FABP4) is an essential driver for the progression of metabolic-related inflammatory diseases including obesity, diabetes, atherosclerosis, and various lipid metabolism-related tumors. However, FABP4 inhibitors are not yet available for clinical use, which may be associated with their poor selectivity of FABP3, unsatisfactory efficacy and physicochemical properties. Herein, we reported a systematic optimization of a class of biphenyl scaffold molecules as potent FABP4 inhibitors. Further in vitro and in vivo pharmacokinetic studies identified a selective and orally bioavailable compound 10g, with K_i of 0.51 μM against FABP4, K_i of 33.01 μM against FABP3 and bioavailability F% value of 89.4%. In vivo anti-inflammatory efficacy and multi-organ protection study in LPS-induced inflammatory mice model highlighted the potential of compound 10g as a therapeutic candidate in inflammation-related diseases.

FABP4 Expression in Subcutaneous Adipose Tissue Is Independently Associated with Circulating Triglycerides in Obesity

Hypertriglyceridemia (HTG) has been associated with an increased risk of pancreatitis and cardiovascular disease. Adipose tissue plays a major role in lipid metabolism, mobilization and distribution. We have compared the histological and transcriptomic profiles of the subcutaneous (SAT) and visceral (VAT) adipose tissues from subjects with severe obesity undergoing bariatric surgery with (Ob-HTG, n = 37) and without HTG (Ob-NTG, n = 67). Mean age and BMI were 51.87 ± 11.21 years, 45.78 ± 6.96 kg/m² and 50.03 ± 10.17 years, 44.04 ± 4.69 kg/m², respectively. The Ob-HTG group showed higher levels of glycosylated hemoglobin, fasting plasma glucose, high-sensitivity C-reactive protein and prevalence of hypertension. The degree of fibrosis was increased by 14% in SAT from the Ob-HTG group (p = 0.028), while adipocyte size distribution was comparable. Twenty genes were found differentially expressed in SAT and VAT between study groups. Among them, only SAT expression of FABP4 resulted significantly associated with circulating triglyceride levels after adjusting for other covariates and independently explained 5% of the variance in triglyceride levels in the combined model. This relationship was not found in the cohort of lean or overweight patients with normotriglyceridemia (non-Ob, n = 21). These results emphasize the contribution of SAT to triglyceride concentrations in obesity and indicate that FABP4 may be a potential drug target for the treatment of HTG.

Proteomic Analysis Identifies Molecular Players and Biological Processes Specific to SARS-CoV-2 Exposure in Endothelial Cells

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been responsible for the severe pandemic of acute respiratory disease, coronavirus disease 2019 (COVID-19), experienced in the 21st century. The clinical manifestations range from mild symptoms to abnormal blood coagulation and severe respiratory failure. In severe cases, COVID-19 manifests as a thromboinflammatory disease. Damage to the vascular compartment caused by SARS-CoV-2 has been linked to thrombosis, triggered by an enhanced immune response. The molecular mechanisms underlying endothelial activation have not been fully elucidated. We aimed to identify the proteins correlated to the molecular response of human umbilical vein endothelial cells (HUVECs) after exposure to SARS-CoV-2, which might help to unravel the molecular mechanisms of endothelium activation in COVID-19. In this direction, we exposed HUVECs to SARS-CoV-2 and analyzed the expression of specific cellular receptors, and changes in the proteome of HUVECs at different time points. We identified that HUVECs exhibit non-productive infection without cytopathic effects, in addition to the lack of expression of specific cell receptors known to be essential for SARS-CoV-2 entry into cells. We highlighted the enrichment of the protein SUMOylation pathway and the increase in SUMO2, which was confirmed by orthogonal assays. In conclusion, proteomic analysis revealed that the exposure to SARS-CoV-2 induced oxidative stress and changes in protein abundance and pathways enrichment that resembled endothelial dysfunction.

Fatty acid-binding protein 4 in kidney diseases: From mechanisms to clinics

Considerable evidence indicated the relationship between fatty acid-binding protein 4 (FABP4) and kidney diseases. FABP4, a small molecular lipid chaperone, is identified to regulate fatty acid oxidation, inflammation, apoptosis, endoplasmic reticulum stress and macrophage-to-myofibroblast transition in kidney diseases. Many studies have shown that circulating FABP4 level is related to proteinuria, renal function decline, cardiovascular complications of end-stage renal disease and even the prognosis of kidney transplanted patients. Notably, pharmacological or genetic inhibition of FABP4 attenuated renal injury in the various experimental models of kidney diseases, making it promising to develop potential therapeutic strategies targeting FABP4 in kidney diseases. In this study, we updated and reviewed the mechanisms and clinical significance of FABP4 in kidney diseases.

Inflammatory and metabolic markers in relation to outcome of in vitro fertilization in a cohort of predominantly overweight and obese women

For overweight and obese women undergoing in vitro fertilization (IVF) the pregnancy and live birth rates are compromised while the underlying mechanisms and predictors are unclear. The aim was to explore the association between adipose tissue-related inflammatory and metabolic markers and the pregnancy and live birth outcome of IVF in a cohort of predominantly overweight and obese women. Serum samples, fulfilling standardizing criteria, were identified from 195 women having participated in either the control (n = 131) or intervention (n = 64) group of a randomized controlled trial (RCT), seeking to evaluate the effect of a weight reduction intervention on IVF outcome in obese women. Serum high-sensitivity C-reactive protein (hsCRP) and the adipokines leptin and adipocyte fatty acid-binding protein (AFABP) were analyzed for the whole cohort (n = 195) in samples collected shortly before IVF [at randomization (control group), after intervention (intervention group)]. Information on age, anthropometry [BMI, waist circumference, waist-to-height ratio (WHtR)], pregnancy and live birth rates after IVF, as well as the spontaneous pregnancy rate, was extracted or calculated from collected data. The women of the original intervention group were also characterized at randomization regarding all variables. Eight women [n = 3 original control group (2.3%), n = 5 original intervention group (7.8%)] conceived spontaneously before starting IVF. BMI category proportions in the cohort undergoing IVF (n = 187) were 1.6/20.1/78.3% (normal weight/overweight/obese). The pregnancy and live birth rates after IVF for the cohort were 35.8% (n = 67) and 24.6% (n = 46), respectively. Multivariable logistic regression revealed that none of the variables (age, hsCRP, leptin, AFABP, BMI, waist circumference, WHtR) were predictive factors of pregnancy or live birth after IVF. Women of the original intervention group displayed reductions in hsCRP, leptin, and anthropometric variables after intervention while AFABP was unchanged. In this cohort of predominantly overweight and obese women undergoing IVF, neither low-grade inflammation, in terms of hsCRP, other circulating inflammatory and metabolic markers released from adipose tissue (leptin, AFABP), nor anthropometric measures of adiposity or adipose tissue distribution (BMI, waist, WHtR) were identified as predictive factors of pregnancy or live birth rate.Trial registration: ClinicalTrials.gov number, NCT01566929. Trial registration date 30-03-2012, retrospectively registered.

Serum adipocyte fatty acid-binding protein level is positively associated with aortic stiffness in nondialysis chronic kidney disease patients: A cross-sectional study

Aortic stiffness (AS) is a major predictor of cardiovascular disease and mortality in patients with chronic kidney disease (CKD) and adipocyte fatty acid-binding protein (A-FABP) is a novel adipokine that is positively correlated with AS in the general population. Therefore, we investigated the correlation between serum A-FABP levels and AS in nondialysis CKD patients. Fasting blood samples and baseline characteristics were obtained in 270 patients with nondialysis CKD. Serum A-FABP concentrations were determined by enzyme immunoassay and carotid-femoral pulse wave velocity (cfPWV) measurements were acquired using a validated tonometry system. Patients with cfPWV >10 m/s formed the AS group, while those with values ≤10 m/s comprised the comparison group. Among 270 CKD patients, 92 patients (34.1%) were in the AS group. Compared to those in the comparison group, patients in the AS group were older (P < .001), had a higher prevalence of diabetes, along with higher serum A-FABP level (P < .001), larger waist circumference (P = .004), and lower estimated glomerular filtration rate (P = .001) but higher levels of body fat mass (P = .010), systolic blood pressure (P < .001), fasting glucose (P = .014), blood urea nitrogen (P = .009), and serum creatinine (P = .004). The serum log-A-FABP level was positively associated with log-cfPWV (β = 0.178, P = .001) in nondialysis CKD patients and multivariable logistic regression analysis identified serum A-FABP (P = .006), age (P = .001), and systolic blood pressure (P = .015) as independent predictors of AS in nondialysis-dependent CKD patients. Elevated A-FABP levels may be a significant predictor of AS in nondialysis CKD patients.

Fatty Acid-Binding Protein 4 in Patients with and without Diabetic Retinopathy

BACKGROUND

Fatty acid-binding protein 4 (FABP4) has been demonstrated to be a predictor of early diabetic nephropathy. However, little is known about the relationship between FABP4 and diabetic retinopathy (DR). This study explored the value of FABP4 as a biomarker of DR in patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 238 subjects were enrolled, including 20 healthy controls and 218 T2DM patients. Serum FABP4 levels were measured using a sandwich enzyme-linked immunosorbent assay. The grade of DR was determined using fundus fluorescence angiography. Based on the international classification of DR, all T2DM patients were classified into the following three subgroups: non-DR group, non-proliferative diabetic retinopathy (NPDR) group, and proliferative diabetic retinopathy (PDR) group. Multivariate logistic regression analyses were employed to assess the correlation between FABP4 levels and DR severity.

RESULTS

FABP4 correlated positively with DR severity (r=0.225, P=0.001). Receiver operating characteristic curve analysis was used to assess the diagnostic potential of FABP4 in identifying DR, with an area under the curve of 0.624 (37% sensitivity, 83.6% specificity) and an optimum cut-off value of 76.4 μg/L. Multivariate logistic regression model including FABP4 as a categorized binary variable using the cut-off value of 76.4 μg/L showed that the concentration of FABP4 above the cut-off value increased the risk of NPDR (odds ratio [OR], 3.231; 95% confidence interval [CI], 1.574 to 6.632; P=0.001) and PDR (OR, 3.689; 95% CI, 1.306 to 10.424; P=0.014).

CONCLUSION

FABP4 may be used as a serum biomarker for the diagnosis of DR.

Downregulation of fatty acid binding protein 4 alleviates lipid peroxidation and oxidative stress in diabetic retinopathy by regulating peroxisome proliferator-activated receptor γ-mediated ferroptosis

This study aims to explore the role of fatty acid binding protein 4 (FABP4) in diabetic retinopathy (DR), and to elucidate the potential regulatory mechanism. We firstly developed a mouse model of DR by injection with streptozocin (STZ) into C57BL/6 male mice and a cell model of DR by induction of high glucose (HG) to ARPE-19 cells. BMS309403, an inhibitor of FABP4, was employed for treatment. The blood glucose in vivo was monitored and the histological changes of retinal tissues were observed by hematoxylin and eosin staining and Evans blue assay. The expression level of FABP4 was detected by western blot and Immunohistochemical staining. The critical factors related to lipid peroxidation and oxidative stress were detected using their commercial kits, respectively. Prussian blue staining, iron content assay and thiobarbituric acid-reactive substances (TBARS) assay were conducted to evaluate ferroptosis. As a result, FABP4 was elevated in retina and serum of STZ-induced mice and in HG-induced ARPE-19 cells. BMS309403 treatment notably alleviated reduced blood glucose, reduced histological damage, and vascular permeability. In addition, BMS309403 treatment inhibited lipid peroxidation, oxidative stress, and ferroptosis both in vivo and in vitro. Furthermore, BMS309403 promoted the activation of peroxisome proliferator-activated receptor γ (PPARγ). GW9662 (an inhibitor of PPARγ) or Erastin (an inducer of ferroptosis) partially weakened the suppressive effects of BMS309403 on HG-induced lipid peroxidation, oxidative stress and ferroptosis. Taken together, FABP4 inhibition alleviates lipid peroxidation and oxidative stress in DR by regulating PPARγ-mediated ferroptosis.

Age and Serum Adipocyte Fatty-Acid-Binding Protein Level Are Associated with Aortic Stiffness in Coronary Artery Bypass Graft Patients

Old age has been proven to be related to progressed arterial or aortic stiffness. Aortic stiffness is an independent predictor of all-cause and cardiovascular disease mortalities in patients who have undergone coronary artery bypass grafting (CABG) surgery. Higher serum concentrations of adipocyte fatty-acid-binding protein (A-FABP) could be considered a predictor of aortic stiffness in patients with hypertension or diabetes mellitus. This study aims to investigate the relationships between A-FABP and aortic stiffness in patients who have received CABG. A total of 84 CABG patients were enrolled in our study from September 2018 to May 2019. Serum A-FABP levels were determined using a commercial enzyme immunoassay. Carotid−femoral pulse wave velocity (cfPWV) > 10 m/s was defined as aortic stiffness. Of the 84 CABG patients, 28 (33.3%) with aortic stiffness had a higher average age; exhibited higher rates of diabetes; and had higher serum creatinine, C-reactive protein, and A-FABP levels compared to controls. Multivariable logistic regression revealed that serum A-FABP levels (odds ratio (OR) = 1.068, 95% confidence interval (CI) 1.017−1.121, p = 0.008) and age (OR = 1.204, 95% CI 1.067−1.359, p = 0.003) were independent predictors of aortic stiffness. Multivariable stepwise linear regression revealed significant positive correlations of age and A-FABP levels with cfPWV values. Serum A-FABP level is positively correlated with cfPWV values, and a high serum A-FABP level is associated with aortic stiffness in patients who have undergone CABG.

Adipokines as New Biomarkers of Immune Recovery: Apelin Receptor, RBP4 and ZAG Are Related to CD4+ T-Cell Reconstitution in PLHIV on Suppressive Antiretroviral Therapy

A significant proportion of people living with HIV (PLHIV) who successfully achieve virological suppression fail to recover CD4⁺ T-cell counts. Since adipose tissue has been discovered as a key immune organ, this study aimed to assess the role of adipokines in the HIV immunodiscordant response. This is a multicenter prospective study including 221 PLHIV starting the first antiretroviral therapy (ART) and classified according to baseline CD4⁺ T-cell counts/µL (controls > 200 cells/µL and cases ≤ 200 cells/µL). Immune failure recovery was considered when cases did not reach more than 250 CD4⁺ T cells/µL at 144 weeks (immunological nonresponders, INR). Circulating adipokine concentrations were longitudinally measured using enzyme-linked immunosorbent assays. At baseline, apelin receptor (APLNR) and zinc-alpha-2-glycoprotein (ZAG) concentrations were significantly lower in INRs than in immunological responders (p = 0.043 and p = 0.034), and they remained lower during all ART follow-up visits (p = 0.044 and p = 0.028 for APLNR, p = 0.038 and p = 0.010 for ZAG, at 48 and 144 weeks, respectively). ZAG levels positively correlated with retinol-binding protein 4 (RBP4) levels (p < 0.01), and low circulating RBP4 concentrations were related to a low CD4⁺ T-cell gain (p = 0.018 and p = 0.039 at 48 and 144 weeks, respectively). Multiple regression adjusted for clinical variables and adipokine concentrations confirmed both low APLNR and RBP4 as independent predictors for CD4⁺ T cells at 144 weeks (p < 0.001). In conclusion, low APLNR and RBP4 concentrations were associated with poor immune recovery in treated PLHIV and could be considered predictive biomarkers of a discordant immunological response.

Soybean diacylglycerol regulates lipid metabolism in D-galactose-induced aging rats by altering gut microbiota and gene expression of colonic epithelial cells

Lipid metabolism is closely related to the health of aging bodies and its disorder often leads to cardiovascular diseases and chronic diseases. Dietary fat is one of the important sources of body fat, which affects the body's lipid metabolism. However, how dietary fat affects lipid metabolism in aging bodies has not been reported. Thus, the effects of soybean diacylglycerol (DAG) on lipid metabolism in D-galactose-induced aging rats were investigated by detecting the serum biochemical indexes, hepatocyte morphology, gut microbiota changes, and gene expression of colonic epithelial cells. The results showed that DAG alleviated the lipid metabolism disorders, and the hepatocyte morphology of aging rats fed DAG was normal. 16S rDNA analysis showed that DAG restored Eisenbergiella and Veillonella that were missing in aging rats. The relative abundances of Romboutsia and Ruminococcus_2 decreased and the relative abundance of Lachnospiraceae NK4A136 group increased significantly with the influence of DAG (P < 0.05). Gene expression profiles showed that the gene expression of colon epithelial cells was altered by DAG and DAG downregulated the genes Lipe and Fabp4 related to the lipolysis of adipocytes. In conclusion, DAG regulated the lipid metabolism of aging rats by regulating gut microbiota and gene expression of colonic epithelial cells.

Fatty acid-binding protein 4: a key regulator of ketoacidosis in new-onset type 1 diabetes

AIMS/HYPOTHESIS

Fatty acid-binding protein 4 (FABP4) is an adipokine with a key regulatory role in glucose and lipid metabolism. We prospectively evaluated the role of FABP4 in the pathophysiology of diabetic ketoacidosis (DKA) in new-onset type 1 diabetes.

METHODS

Clinical and laboratory data were prospectively collected from consecutive children presenting with new-onset type 1 diabetes. In addition to blood chemistry and gases, insulin, C-peptide, serum FABP4 and NEFA were collected upon presentation and 48 h after initiation of insulin treatment. In a mouse model of type 1 diabetes, glucose, insulin, β-hydroxybutyrate and weight were compared between FABP4 knockout (Fabp4^-/-) and wild-type (WT) mice.

RESULTS

Included were 33 children (mean age 9.3 ± 3.5 years, 52% male), of whom 14 (42%) presented with DKA. FABP4 levels were higher in the DKA group compared with the non-DKA group (median [IQR] 10.1 [7.9-14.2] ng/ml vs 6.3 [3.9-7] ng/ml, respectively; p = 0.005). The FABP4 level was positively correlated with HbA_1c at presentation and inversely correlated with venous blood pH and bicarbonate levels (p < 0.05 for all). Following initiation of insulin therapy, a marked reduction in FABP4 was observed in all children. An FABP4 level of 7.22 ng/ml had a sensitivity of 86% and a specificity of 78% for the diagnosis of DKA, with an area under the receiver operating characteristic curve of 0.78 (95% CI 0.6, 0.95; p = 0.008). In a streptozotocin-induced diabetes mouse model, Fabp4^-/- mice exhibited marked hypoinsulinaemia and hyperglycaemia similar to WT mice but displayed no significant increase in β-hydroxybutyrate and were protected from ketoacidosis.

CONCLUSIONS/INTERPRETATION

FABP4 is suggested to be a necessary regulator of ketogenesis in insulin-deficient states.

Dysfunction of metabolic activity of bone marrow mesenchymal stem cells in aged mice

Objectives

Evidences have suggested that the metabolic function is the key regulator to the fate of MSCs, but its function in senescence of MSC and the underlying mechanism is unclear. Therefore, the purpose of this study was to investigate the metabolic activity of MSCs and its possible mechanism during aging.

Materials and Methods

We used the Seahorse XF24 Analyzer to understand OCR and ECAR in BMSCs and used RT‐PCR to analyze the gene expression of mitochondrial biogenesis and key enzymes in glycolysis. We analyzed BMSC mitochondrial activity by MitoTracker Deep Red and JC‐1 staining, and detected NAD+/NADH ratio and ATP levels in BMSCs. Microarray and proteomic analyses were performed to detect differentially expressed genes and proteins in BMSCs. The impact of aging on BMSCs through mitochondrial electron transport chain (ETC) was evaluated by Rotenone and Coenzyme Q10.

Results

Our results demonstrated that the oxidative phosphorylation and glycolytic activity of BMSCs in aged mice were significantly decreased when compared with young mice. BMSCs in aged mice had lower mitochondrial membrane potential, NAD+/NADH ratio, and ATP production than young mice. FABP4 may play a key role in BMSC senescence caused by fatty acid metabolism disorders.

Conclusions

Taken together, our results indicated the dysfunction of the metabolic activity of BMSCs in aged mice, which would play the important role in the impaired biological properties. Therefore, the regulation of metabolic activity may be a potential therapeutic target for enhancing the regenerative functions of BMSCs.

Unveiling the Role of the Fatty Acid Binding Protein 4 in the Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD), the main cause of chronic liver disease worldwide, is a progressive disease ranging from fatty liver to steatohepatitis (metabolic-associated steatohepatitis; MASH). Nevertheless, it remains underdiagnosed due to the lack of effective non-invasive methods for its diagnosis and staging. Although MAFLD has been found in lean individuals, it is closely associated with obesity-related conditions. Adipose tissue is the main source of liver triglycerides and adipocytes act as endocrine organs releasing a large number of adipokines and pro-inflammatory mediators involved in MAFLD progression into bloodstream. Among the adipocyte-derived molecules, fatty acid binding protein 4 (FABP4) has been recently associated with fatty liver and additional features of advanced stages of MAFLD. Additionally, emerging data from preclinical studies propose FABP4 as a causal actor involved in the disease progression, rather than a mere biomarker for the disease. Therefore, the FABP4 regulation could be considered as a potential therapeutic strategy to MAFLD. Here, we review the current knowledge of FABP4 in MAFLD, as well as its potential role as a therapeutic target for this disease.

Causative Mechanisms of Childhood and Adolescent Obesity Leading to Adult Cardiometabolic Disease: A Literature Review

The past few decades have shown a worrisome increase in the prevalence of obesity and its related illnesses. This increasing burden has a noteworthy impact on overall worldwide mortality and morbidity, with significant economic implications as well. The same trend is apparent regarding pediatric obesity. This is a particularly concerning aspect when considering the well-established link between cardiovascular disease and obesity, and the fact that childhood obesity frequently leads to adult obesity. Moreover, most obese adults have a history of excess weight starting in childhood. In addition, given the cumulative character of both time and severity of exposure to obesity as a risk factor for associated diseases, the repercussions of obesity prevalence and related morbidity could be exponential in time. The purpose of this review is to outline key aspects regarding the current knowledge on childhood and adolescent obesity as a cardiometabolic risk factor, as well as the most common etiological pathways involved in the development of weight excess and associated cardiovascular and metabolic diseases.

Fatty acid-binding protein 4 circulating levels in non-segmental vitiligo

Background

Vitiligo is an acquired and progressive mucocutaneous disease resulting from the loss of active epidermal melanocytes. Metabolic syndrome (MetS) affects about 25% of the world’s population and is linked to inflammatory skin diseases including vitiligo. Fatty Acid-Binding Protein 4 (FABP4) is an intracellular lipid chaperone. FABP4 is closely associated with MetS.

Objectives

To evaluate the serum level of FABP4 in vitiligo patients and its relation to MetS in the investigated cases.

Methods

This case control study was conducted on 45 patients having non segmental vitiligo and 45 matched controls. Their lipid profile, blood glucose and serum FABP4 levels were measured.

Results

There were significant elevations in FABP4 (p < 0.001), cholesterol (p < 0.001), triglycerides (p = 0.005), and glucose (fasting [p = 0.001] and 2 hours post prandial [p < 0.001]) levels in patients in comparison with controls. MetS was significantly more prevalent among vitiligo patients (p < 0.001) and associated with high FABP4 serum levels (p = 0.037). In vitiligo patients, there were significant positive correlations between FABP4 serum levels and triglycerides (p = 0.047), cholesterol (p = 0.001) and LDL (p = 0.001) levels and negative correlation regarding HDL level (p = 0.009). FABP4 level was a significantly good diagnostic test for early detection of vitiligo (p < 0.001).

Study limitations

The small number of studied subjects.

Conclusions

FABP4 may play an active role in the disease process of vitiligo that could be mediated through associated dyslipidemia and hyperglycemia. FABP4 may be a marker of vitiligo helping in its early diagnosis, but it does not appear to be useful for determining vitiligo severity, activity or associated MetS.

Association of adipocyte fatty acid-binding protein and tumor necrosis factor alpha with periodontal health and disease: A cross-sectional investigation

Background

Adipocyte fatty acid binding protein (A-FABP) is a novel biomarker of inflammation for various chronic systemic diseases. Since periodontitis is a chronic inflammatory disease, this study explores the association of A-FABP with periodontal disease parameters and tumor necrosis factor-alpha (TNF-α) levels in gingival crevicular fluid in periodontal health and disease.

Materials and Methods

This original research article describes a cross-sectional study conducted at the Department of Periodontics, M. R. Ambedkar Dental College and Hospital, Bangalore, India. This cross-sectional investigation was conducted on sixty subjects which were divided into three groups of twenty subjects each - healthy, gingivitis, and chronic periodontitis. Clinical parameters - plaque index, bleeding index, probing depth, and clinical attachment loss were recorded. Gingival crevicular fluid samples were analyzed for A-FABP and TNF-α levels using ELISA. One-way analysis of variance was used to find the significance of study parameters on a continuous scale between three groups. Pearson's correlation has been used to find the relationship between Gingival crevicular fluid concentration of markers and periodontal parameters. Multiple linear regression analysis was applied to the study. The statistical significance was considered at P < 0.05.

Results

Mean concentration of A-FABP (6.43 ± 2.51) and TNF-α (3454.82 ± 1566.44) was highest in the periodontitis group, and the difference among the groups was statistically significant (P < 0.05). A positive correlation was observed between clinical attachment loss and the two markers among all groups. The correlation between A-FABP and TNF-α in periodontitis groups was positive and statistically significant (P < 0.05). Multiple linear regression model was statistically significant (P < 0.05) indicating that there is a significant relationship between the set of predictors and the clinical attachment loss.

Conclusion

A-FABP and TNF-α levels in GCF were significantly elevated in the presence of inflammation. A-FABP has a probable stimulatory effect on TNF-α; however, its role needs to be explored. A-FABP could serve as a novel inflammatory biomarker of periodontitis and the scope of using A-FABP inhibition as a treatment modality could be investigated with interventional studies.

MiR-208b Regulates Rabbit Preadipocyte Proliferation and Differentiation

microRNAs (miRNAs) play an important role in gene regulation in animals by pairing with target gene mRNA. Many miRNAs are differentially expressed in the adipose tissue, often with conserved expression. In our study, we found that miR-208b expression was observed differently in the preadipocyte differentiation model. When miR-208b was overexpressed in the preadipocyte differentiation model, the overexpressed group displayed higher expression of PPARγ and FABP4—the markers of preadipocyte differentiation. Oil Red O staining revealed that the count of lipid droplets was increased in the overexpressed group. When the expression of miR-208b was inhibited, the above indicators showed an opposite trend. Moreover, results from both 5-ethynyl-2′-deoxyuridine (EDU) and cell counting kit (CCK) analysis showed that miR-208b promoted the proliferation of preadipocyte. Expression of gene CSNK2A2, a direct miR-208b target, was downregulated in the overexpressed group, providing a possible link to multiple signal pathways. Overall, our data indicate that miR-208b play a positive regulatory effect on the proliferation and differentiation of rabbit preadipocyte.

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.

The prediction of Metabolic Syndrome alterations is improved by combining waist circumference and handgrip strength measurements compared to either alone

Background

Adiposity is a major component of the metabolic syndrome (MetS), low muscle strength has also been identified as a risk factor for MetS and for cardiovascular disease. We describe the prevalence of MetS and evaluate the relationship between muscle strength, anthropometric measures of adiposity, and associations with the cluster of the components of MetS, in a middle-income country.

Methods

MetS was defined by the International Diabetes Federation criteria. To assess the association between anthropometric variables (waist circumference (WC), waist-to-hip ratio (W/H), body mass index (BMI)), strength (handgrip/kg bodyweight (HGS/BW)) and the cluster of MetS, we created a MetS score. For each alteration (high triglycerides, low HDLc, dysglycemia, or high blood pressure) one point was conferred. To evaluate the association an index of fat:muscle and MetS score, participants were divided into 9 groups based on combinations of sex-specific tertiles of WC and HGS/BW.

Results

The overall prevalence of MetS in the 5,026 participants (64% women; mean age 51.2 years) was 42%. Lower HGS/BW, and higher WC, BMI, and W/H were associated with a higher MetS score. Amongst the 9 HGS/BW:WC groups, participants in the lowest tertile of HGS/BW and the highest tertile of WC had a higher MetS score (OR = 4.69 in women and OR = 8.25 in men;p < 0.01) compared to those in the highest tertile of HGS/BW and in the lowest tertile of WC.

Conclusion

WC was the principal risk factor for a high MetS score and an inverse association between HGS/BW and MetS score was found. Combining these anthropometric measures improved the prediction of metabolic alterations over either alone.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01256-z.

Inhibition of Fatty Acid Binding Protein 4 in Obese Male Mice Adversely Affects Reproductive Parameters

Background:

As obesity is increasing worldwide, obese people use various methods to get rid of excess weight. BMS309403 (A drug) is a specific inhibitor of fatty acid binding protein 4. In this study, the effects of the BMS309403 on serum biochemical markers, testis tissue spermatogenesis and apoptotic markers were investigated in male mice.

Methods:

Balb/c mice (total=56, each group n=14) were divided into control, obese control, obese solvent and obese drug groups. The obese control, obese solvent and obese drug groups were fed on the high sucrose diet to lead to obesity. After the development of obesity, BMS309403 was orally administered to the obese drug group for six weeks. It was performed in testicular tissues (Johnson Score and apoptosis markers) and biochemical tests (total testosterone, sex hormone binding globulin, inhibin-B tests and free androgen index) were used to evaluate reproductive parameters. The p<0.05 was considered to indicate a statistical significance.

Results:

Serum fatty acid binding protein 4 levels were higher in obese control group and obese solvent group, compared to control (p<0.05) and obese drug groups (p<0.001). Serum total testosterone, free androgen index, inhibin-B, sex hormone binding globulin levels, testicular tissue B-cell lymphoma-2 expression level and Johnson Score parameters were lower in all obese groups compared with the control group. Inhibin-B levels and Johnson Score results were lower in obese drug group compared to other two obese groups (p<0.05).

Conclusion:

Contrary to expectations, the use of BMS309403 negatively affected male reproductive parameters. Negative changes in reproductive parameters may be a result of the increased lee index of obesity.

Serum Levels of Adipocyte Fatty Acid-Binding Protein Are Associated with Rapid Renal Function Decline in Patients with Type 2 Diabetes Mellitus and Preserved Renal Function

BACKGROUND

Recent studies have demonstrated that the levels of adipocyte fatty acid-binding protein (A-FABP) are closely associated with diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM). This study aimed to examine the association between serum A-FABP level and rapid renal function decline in patients with T2DM and preserved renal function.

METHODS

This was a prospective observational study of 452 patients with T2DM and preserved renal function who had serial measurements of estimated glomerular filtration rate (eGFR). Rapid renal function decline was defined as an eGFR decline of >4% per year. The association between baseline serum A-FABP level and rapid renal function decline was investigated.

RESULTS

Over a median follow-up of 7 years, 82 participants (18.1%) experienced rapid renal function decline. Median A-FABP levels were significantly higher in patients with rapid renal function decline, compared to non-decliners (20.2 ng/mL vs. 17.2 ng/mL, P=0.005). A higher baseline level of A-FABP was associated with a greater risk of developing rapid renal function decline, independent of age, sex, duration of diabetes, body mass index, systolic blood pressure, history of cardiovascular disease, baseline eGFR, urine albumin creatinine ratio, total cholesterol, glycosylated hemoglobin, high-sensitivity C-reactive protein and use of thiazolidinedione, insulin, angiotensin-converting-enzyme inhibitors and angiotensin II-receptor blockers and statin (odds ratio, 3.10; 95% confidence interval, 1.53 to 6.29; P=0.002).

CONCLUSION

A high level of serum A-FABP is associated with an increased risk of rapid renal function decline in patients with T2DM and preserved renal function. This suggests that A-FABP could play a role in the progression of DKD in the early stages.

Elevated expression of FABP4 is associated with disease activity in rheumatoid arthritis patients

Aim: Data from 124 rheumatoid arthritis (RA) patients and 69 healthy controls were collected. Materials & methods: ELISA was performed to detect serum FABP4 levels. Results: FABP4 level was elevated in RA patients and positively associated with 28-joint disease activity score, high-sensitivity C-reactive protein, erythrocyte sedimentation rate, total cholesterol, triglyceride and low-density lipoprotein cholesterol. Additionally, the area under the receiver operating characteristic curve for FABP4 was 0.685 for RA patients versus healthy controls (p = 0.001). RA patients were separated into low, moderate and high disease activity based on 28-joint disease activity score. The area under the receiver operating characteristic value was 0.877 for RA patients with high disease activity versus healthy controls (p < 0.001). Conclusion: FABP4 was associated with disease activity in RA patients.

Associations between High Serum Adipocyte Fatty Acid Binding Protein and First Hospitalization in Kidney Transplantation Patients: A 5-Year Follow-up Study

Adipocyte fatty acid binding protein (A-FABP) is predictive of type 2 diabetes mellitus incidences and metabolic syndrome and is independently associated with atherosclerosis. The present study aimed to assess the association between serum A-FABP levels and future first hospitalization events in kidney transplantation (KT). We enrolled 72 KT patients from January through April 2012 and followed up on these subjects until June 2017. The first hospitalization events incidence was the primary endpoint. Using a commercially available enzyme immunoassay, serum A-FABP levels were measured from the patient's fasting blood samples. During a median 65-month follow-up, 49 first hospitalization events occurred. KT patients with first hospitalization events had greater incidences of hypertension, diabetes, and higher serum blood urea nitrogen, creatinine, triglyceride, and A-FABP levels than those without the events. Kaplan-Meier analysis showed that the cumulative incidence of first hospitalization events was greater in the high A-FABP group than in the low A-FABP group. Multivariate Cox analysis with significant variables showed that serum A-FABP (hazard ratio = 1.012; 95% confidence interval = 1.000-1.025; p = 0.044) was independently associated with first hospitalization events among KT patients. The results revealed that serum A-FABP is associated with first hospitalization events in KT patients. However, further prospective studies are needed to determine the mechanisms underlying this association.

Deoxynivalenol Exposure Suppresses Adipogenesis by Inhibiting the Expression of Peroxisome Proliferator-Activated Receptor Gamma 2 (PPARγ2) in 3T3-L1 Cells

Deoxynivalenol (DON)-a type B trichothecene mycotoxin, mainly produced by the secondary metabolism of Fusarium-has toxic effects on animals and humans. Although DON's toxicity in many organs including the adrenal glands, thymus, stomach, spleen, and colon has been addressed, its effects on adipocytes have not been investigated. In this study, 3T3-L1 cells were chosen as the cell model and treated with less toxic doses of DON (100 ng/mL) for 7 days. An inhibition of adipogenesis and decrease in triglycerides (TGs) were observed. DON exposure significantly downregulated the expression of PPARγ2 and C/EBPα, along with that of other adipogenic marker genes in 3T3-L1 cells and BALB/c mice. The anti-adipogenesis effect of DON and the downregulation of the expression of adipogenic marker genes were effectively reversed by PPARγ2 overexpression. The repression of PPARγ2's expression is the pivotal event during DON exposure regarding adipogenesis. DON exposure specifically decreased the di-/trimethylation levels of Histone 3 at lysine 4 in 3T3-L1 cells, therefore weakening the enrichment of H3K4me2 and H3K4me3 at the Pparγ2 promoter and suppressing its expression. Conclusively, DON exposure inhibited PPARγ2 expression via decreasing H3K4 methylation, downregulated the expression of PPARγ2-regulated adipogenic marker genes, and consequently suppressed the intermediate and late stages of adipogenesis. Our results broaden the current understanding of DON's toxic effects and provide a reference for addressing the toxicological mechanism of DON's interference with lipid homeostasis.

Using proximity extension proteomics assay to discover novel biomarkers associated with circulating leptin levels in patients with type 2 diabetes

We aimed to discover novel associations between leptin and circulating proteins which could link leptin to the development of cardiovascular disease in patients with type 2 diabetes (T2DM). In a discovery phase, we investigated associations between 88 plasma proteins, assessed with a proximity extension assay, and plasma leptin in a cohort of middle-aged patients with T2DM. Associations passing the significance threshold of a False discovery rate of 5% (corresponding to p < 0.0017) were replicated in patients with T2DM in an independent cohort. We also investigated if proteins mediated the longitudinal association between plasma leptin and the incidence of major cardiovascular events (MACE). One protein, adipocyte fatty acid binding protein (A-FABP), was significantly associated with leptin in both the discovery phase [95% CI (0.06, 0.17) p = 0.00002] and the replication cohort [95% CI (0.12, 0.39) p = 0.0003]. Multiplicative interaction analyses in the two cohorts suggest a stronger association between A-FABP and leptin in men than in women. In longitudinal analyses, the association between leptin and MACE was slightly attenuated after adding A-FABP to the multivariate model. Our analysis identified a consistent association between leptin and A-FABP in two independent cohorts of patients with T2DM, particularly in men.Trial registration: ClinicalTrials.gov identifier NCT01049737.

Role of Fatty Acid Binding Protein 4 (FABP4) in Kidney Disease

Accumulating evidences indicated that obesity and metabolic syndrome were independent risk factors for the development and progression of kidney diseases. Apart from inflammation, lipotoxicity, and hemodynamic factors, adipokines have been proposed to play crucial roles in the relationship between kidney diseases and metabolic disorders. As one of the key adipokines, fatty acid binding protein 4 (FABP4), which is mainly expressed in adipocytes and macrophages, has recently been shown to be associated with renal dysfunction and kidney damage. Both clinical and experimental studies have proposed circulating FABP4 as a novel predictor for renal injuries, and it might also be a predictor for cardiovascular events in patients with end stage renal disease (ESRD). FABP4 has also been detected in the glomerular cells and epithelial tubular cells in mouse and human kidneys, and the expression of FABP4 in these cells has been involved in the pathogenesis of kidney diseases. In addition, experimental studies suggested that inhibition of FABP4 had protective effects on renal damage. Here, we reviewed current knowledge regarding the role of FABP4 in pathophysiological insights as well as its potential function as a predictor and therapeutic target for kidney diseases.

The Effect of Methanolic Valeriana officinalis Root Extract on Adipocyte Differentiation and Adiponectin Production in 3T3-L1 Adipocytes

Adipose tissue is an endocrine organ and its endocrine function is closely associated with type 2 diabetes mellitus. Valeriana officinalis (Valerian) exerts some physiological effects; however, its influence on adipocytes remains unclear. We investigated the effect of methanolic Valerian root extract (Vale) on 3T3-L1 adipocytes. Vale (1, 10, and 100 μg/mL) dose-dependently promoted adipocyte differentiation with increasing lipid accumulation. In addition, Vale significantly increased the mRNA levels in genes associated with adipocyte differentiation, including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α , and adipocyte protein 2, in dose-dependent manner. Vale also significantly enhanced mRNA and protein levels in adiponectin. A PPARγ antagonist assay and a PPARγ binding assay revealed that Vale-induced increased adipocyte differentiation and adiponectin production were partly associated with direct binding to PPARγ. Valerenic acid, a characteristic component in Valerian, also demonstrated the ability to induce adipocyte differentiation and adiponectin secretion, suggesting that it is one of the functional components in Vale.

Plasma FABP4 is associated with liver disease recovery during treatment-induced clearance of chronic HCV infection

Direct-acting antivirals (DAAs) have dramatically improved the management of chronic hepatitis C (CHC). In this study, we investigated the effects of hepatitis C virus clearance on markers of systemic inflammation measured in plasma samples from CHC patients before, during and after DAA therapy. We identified a plasma soluble protein profile associated with CHC. Successful DAA therapy rapidly normalised the plasma inflammatory milieu, with the notable exception of soluble (s)CD163, a marker of macrophage activation, which remained elevated after viral clearance and segregated patients with high and low levels of cirrhosis. Patients who received DAA in combination with Ribavirin maintained elevated levels of CXCL10, consistent with an immune-stimulatory role of Ribavirin. As anticipated, DAA-treated patients experienced durable improvement in liver fibrosis measurements. Interestingly, pre-treatment levels of fatty acid-binding protein 4 (FABP4) were inversely associated with reduction of APRI and FIB-4 scores during treatment. Together, these results support the notion of a rapid restoration of many aspects of the inflammatory state in CHC patients in response to DAA therapy. Furthermore, the associations with sCD163 and FABP4 warrant further investigation into the role of macrophages in residual liver disease and fibrosis resolution after viral clearance.

The Gene and Protein Expression of the Main Components of the Lipolytic System in Human Myocardium and Heart Perivascular Adipose Tissue. Effect of Coronary Atherosclerosis

The aim of our study was to examine the regulation of triacylglycerols (TG) metabolism in myocardium and heart perivascular adipose tissue in coronary atherosclerosis. Adipose triglyceride lipase (ATGL) is the major TG-hydrolase. The enzyme is activated by a protein called comparative gene identification 58 (CGI-58) and inhibited by a protein called G0/G1 switch protein 2 (G0S2). Samples of the right atrial appendage and perivascular adipose tissue were obtained from two groups of patients: 1—with multivessel coronary artery disease qualified for coronary artery bypass grafting (CAD), 2—patients with no atherosclerosis qualified for a valve replacement (NCAD). The mRNA and protein analysis of ATGL, HSL, CGI-58, G0S2, FABP4, FAT/CD36, LPL, β-HAD, CS, COX4/1, FAS, SREBP-1c, GPAT1, COX-2, 15-LO, and NFκβ were determined by using real-time PCR and Western Blot. The level of lipids (i.e., TG, diacylglycerol (DG), and FFA) was examined by GLC. We demonstrated that in myocardium coronary atherosclerosis increases only the transcript level of G0S2 and FABP4. Most importantly, ATGL, β-HAD, and COX4/1 protein expression was reduced and it was accompanied by over double the elevation in TG content in the CAD group. The fatty acid synthesis and their cellular uptake were stable in the myocardium of patients with CAD. Additionally, the expression of proteins contributing to inflammation was increased in the myocardium of patients with coronary stenosis. Finally, in the perivascular adipose tissue, the mRNA of G0S2 was elevated, whereas the protein content of FABP-4 was increased and for COX4/1 diminished. These data suggest that a reduction in ATGL protein expression leads to myocardial steatosis in patients with CAD.

Reduced airway levels of fatty-acid binding protein 4 in COPD: relationship with airway infection and disease severity

Background

For still unclear reasons, chronic airway infection often occurs in patients with Chronic Obstructive Pulmonary Disease (COPD), particularly in those with more severe airflow limitation. Fatty-acid binding protein 4 (FABP4) is an adipokine involved in the innate immune response against infection produced by alveolar macrophages (Mɸ). We hypothesized that airway levels of FABP4 may be altered in COPD patients with chronic airway infection.

Methods

In this prospective and controlled study we: (1) compared airway FABP4 levels (ELISA) in induced sputum, bronchoalveolar lavage fluid (BALF) and plasma samples in 52 clinically stable COPD patients (65.2 ± 7.9 years, FEV₁ 59 ± 16% predicted) and 29 healthy volunteers (55.0 ± 12.3 years, FEV₁ 97 ± 16% predicted); (2) explored their relationship with the presence of bacterial airway infection, defined by the presence of potentially pathogenic bacteria (PPB) at ≥10³ colony-forming units/ml in BALF; (3) investigated their relationship with the quantity and proportion of Mɸ in BALF (flow cytometry); and, (4) studied their relationship with the severity of airflow limitation (FEV₁), GOLD grade and level of symptoms (CAT questionnaire).

Results

We found that: (1) airway levels of FABP4 (but not plasma ones) were reduced in COPD patients vs. controls [219.2 (96.0–319.6) vs. 273.4 (203.1–426.7) (pg/ml)/protein, p = 0.03 in BALF]; (2) COPD patients with airway infection had lower sputum FABP4 levels [0.73 (0.35–15.3) vs. 15.6 (2.0–29.4) ng/ml, p = 0.02]; (3) in COPD patients, the number and proportion of Mɸ were positively related with FABP4 levels in BALF; (4) BALF and sputum FABP4 levels were positively related with FEV₁, negatively with the CAT score, and lowest in GOLD grade D patients.

Conclusions

Airway FABP4 levels are reduced in COPD patients, especially in those with airway infection and more severe disease. The relationship observed between Mɸ and airway FABP4 levels supports a role for FABP4 in the pathogenesis of airway infection and disease severity in COPD.

Adipocyte Fatty Acid-Binding Protein 4 is Altered in Growth Discordant Dichorionic, but not in Monochorionic Twins

Context

The fetal period has a critical and long-lasting impact on the regulation of metabolic processes and a life-long predisposition for obesity and metabolic syndrome. The exact mechanisms are unknown, but epigenetic regulation likely plays a major role. Twins represent an excellent model to study these mechanisms, as they share the same intrauterine environment and similar or even the same genetic information. We examined cord blood levels of adipocyte fatty-acid binding protein 4 (A-FABP or FABP4), a novel adipokine correlated with obesity and metabolic disease in children and adults.

Objective

To examine A-FABP levels in the cord blood of twins with concordant and discordant growth and in singletons with intrauterine growth restriction (IUGR).

Design

Cohort study of 36 twin pairs (25 growth concordant and 11 growth discordant), and 42 singleton pregnancies (28 IUGR and 13 normally grown controls, 1 HELLP).

Outcome Measures

Cord blood A-FABP levels measured by enzyme-linked immunosorbent assay (ELISA).

Results

A-FABP levels were higher in the smaller of growth discordant dichorionic (DC) twins versus their co-twins (109.46 ± 62.80 ng/mL vs. 72.93 ± 36.66 ng/mL, P = 0.028). A-FABP was negatively correlated with birth weight and gestational age (P < 0.001), but not with birth weight z-score (P = 0.37).

Conclusions

Increased A-FABP levels might be associated with an increased metabolic risk in growth-restricted (twins) and prematurely born infants.

NPY1R-targeted peptide-mediated delivery of a dual PPARα/γ agonist to adipocytes enhances adipogenesis and prevents diabetes progression

Objective

PPARα/γ dual agonists have been in clinical development for the treatment of metabolic diseases including type 2 diabetes and dyslipidemia. However, severe adverse side effects led to complications in clinical trials. As most of the beneficial effects rely on the compound activity in adipocytes, the selective targeting of this cell type is a cutting-edge strategy to develop safe anti-diabetic drugs. The goal of this study was to strengthen the adipocyte-specific uptake of the PPARα/γ agonist tesaglitazar via NPY₁R-mediated internalization.

Methods

NPY₁R-preferring peptide tesaglitazar-[F⁷, P³⁴]-NPY (tesa-NPY) was synthesized by a combination of automated SPPS and manual couplings. Following molecular and functional analyses for proof of concept, cell culture experiments were conducted to monitor the effects on adipogenesis. Mice treated with peptide drug conjugates or vehicle either by gavage or intraperitoneal injection were characterized phenotypically and metabolically. Histological analysis and transcriptional profiling of the adipose tissue were performed.

Results

In vitro studies revealed that the tesaglitazar-[F⁷, P³⁴]-NPY conjugate selectively activates PPARγ in NPY₁R-expressing cells and enhances adipocyte differentiation and adiponectin expression in adipocyte precursor cells. In vivo studies using db/db mice demonstrated that the anti-diabetic activity of the peptide conjugate is as efficient as that of systemically administered tesaglitazar. Additionally, tesa-NPY induces adipocyte differentiation in vivo.

Conclusions

The use of the tesaglitazar-[F7, P34]-NPY conjugate is a promising strategy to apply the beneficial PPARα/γ effects in adipocytes while potentially omitting adverse effects in other tissues.

•

Tesaglitazar-NPY targets adipocytes via NPY₁R receptor-mediated internalization.

•

Peptide-drug conjugate is specifically delivered to NPY₁R-expressing cells.

•

Release of tesaglitazar in adipocytes activates PPARγ.

•

Drug delivery enhances adipocyte differentiation and adiponectin expression.

•

Peptide conjugate exhibits antidiabetic activity in vivo.

High expression of FABP4 and FABP6 in patients with colorectal cancer

Objective

To explore the relationship between FABP4 and FABP6 expression and the pathogenesis of colorectal cancer (CRC) and their potential as biomarkers in the diagnosis of CRC.

Methods

In total, 100 CRC patients and 100 controls were enrolled. The serum levels of FABP4 and FABP6 were detected by enzyme-linked immunosorbent assay (ELISA) before and 2 weeks after radical resection of CRC. The protein expressions of FABP4 and FABP6 were observed in colorectal tumor tissues and adjacent tissues by immunohistochemistry and western blot, respectively. The diagnostic performance of FABP4 and FABP6 in patients with CRC was evaluated by receiver operating characteristic (ROC) curve analysis.

Results

The serum levels of FABP4 and FABP6 in patients with CRC were higher than the levels in the controls before surgery (P < 0.001), and significantly decreased at 2 weeks after operation (P < 0.001). Immunohistochemistry showed that FABP4 and FABP6 were mainly distributed in the cytoplasm of human colorectal tumor tissues, and only a small amount distributed in adjacent tissues. Western blot revealed that the protein expressions of FABP4 and FABP6 were significantly higher in tumor tissues than in adjacent tissues (P < 0.001, P = 0.002, respectively). Tumors with high and low FABP4 and FABP6 expression have no significant correlation in tumor size, tumor site, distant organ and lymph node metastasis, histologic grade, lymphatic permeation, neurological invasion, vascular invasion, and Duke’s and TNM classification. Multivariate logistic regression analysis showed that FABP4 and FABP6 were independent risk factors for CRC (adjusted odds ratio 1.916; 95%CI 1.340–2.492; P < 0.001; adjusted odds ratio 2.162; 95%CI 1.046, 1.078); P < 0.001, respectively). In discriminating CRC from the normal control, the optimal sensitivity of FABP4 and FABP6 were 93.20% (95%CI 87.8–96.7) and 83.70% (95%CI 76.7–89.3), respectively, while the optimal specificity of FABP4 and FABP6 were 48.8% (95%CI 39.8–57.9) and 58.4% (95%CI 49.2–67.1), respectively. When combined detection of serum carcinoembryonic (CEA) and FABP4 and FABP6, the optimal sensitivity and specificity were 61.33% (95%CI 53.0–69.2) and 79.82% (95%CI 71.3–86.8), respectively.

Conclusion

Increased expression of FABP4 and FABP6 not only were strong risk factors for the development of CRC but could also represent a potential biomarker for CRC diagnosis in Chinese patients. Combined detection of CEA with FABP4 and FABP6 could improve the diagnostic efficacy of CRC.

New insights into different adipokines in linking the pathophysiology of obesity and psoriasis

Psoriasis is a chronic, systemic, hyper-proliferative immune-mediated inflammatory skin disease. The results of epidemiological investigations have shown that psoriasis affects around 2% of the general population worldwide, and the total number of psoriasis patients is more than 6 million in China. Apart from the skin manifestations, psoriasis has been verified to associate with several metabolic comorbidities, such as insulin resistance, diabetes and obesity. However, the underlying mechanism is still not elucidated. Adipocytes, considered as the active endocrine cells, are dysfunctional in obesity which displays increased synthesis and secretion of adipokines with other modified metabolic properties. Currently, growing evidence has pointed to the central role of adipokines in adipose tissue and the immune system, providing new insights into the effect of adipokines in linking the pathophysiology of obesity and psoriasis. In this review, we summarize the current understanding of the pathological role of adipokines and the potential mechanisms whereby different adipokines link obesity and psoriasis. Furthermore, we also provide evidence which identifies a potential therapeutic target aiming at adipokines for the management of these two diseases.

Circulating adipocyte fatty acid-binding protein is reduced by continuous positive airway pressure treatment for obstructive sleep apnea-a randomized controlled study

PURPOSE

The circulating level of adipocyte fatty acid-binding protein (AFABP), a biomarker with prognostic and therapeutic importance in metabolic disorders, has been shown to be elevated in obstructive sleep apnea (OSA). This randomized controlled study aimed to investigate the effect of continuous positive airway pressure (CPAP) treatment for OSA on AFABP levels.

METHODS

Consecutive subjects attending sleep study were invited if they were confirmed to have severe OSA and were free of metabolic diseases. Participants were randomized (1:1) into CPAP or observation group for 4 weeks. Demographics, anthropometric data, and circulating biomarkers were checked at baseline and after the 4-week study period.

RESULTS

Ninety subjects were randomized. The mean age was 46 ± 9 years old; 82% were male. Their mean body mass index (BMI) was 29 ± 5 kg/m². By intention-to-treat approach, the CPAP group showed significant reductions in Epworth sleepiness scale and morning systolic blood pressure (- 7.2 mmHg, - 12.7 to - 1.7 mmHg, p = 0.011), but no significant difference in AFABP, adiponectin, C-reactive protein (CRP), and 8-isoprostane levels. In the per-protocol analysis, when only those who were compliant to CPAP were included, a significant reduction in AFABP (- 7.32 ng/ml, - 13.58, - 1.06, p = 0.023) were found in the CPAP-treated group compared with the control group, along with improvements in clinical parameters. Changes in AFABP were independently associated with both systolic blood pressure (β = 0.289, p = 0.028) and diastolic blood pressure (β = 0.217, p = 0.030).

CONCLUSION

CPAP therapy used regularly over 4 weeks for severe OSA lowered circulating AFABP level, suggesting a potential beneficial effect of OSA treatment on alleviating metabolic risks.

TRIAL REGISTRATION

The research protocol was registered at the National Institutes of Health clinical trials registry (NCT01173432).

Adipocyte Fatty Acid-Binding Protein as a Novel Marker of Psoriasis and Clinical Response to Acitretin

Psoriasis is a systemic disease associated with metabolic syndrome and cardiometabolic diseases. Adipocyte fatty acid-binding protein (A-FABP, FABP4) is a relevant mediator of lipid metabolism and several comorbidities development. Aim of the study was to explore the possible role of FABP4 in psoriasis and assess its relationship with disease activity, inflammation or metabolic disturbances, and impact of systemic treatment. Fasting blood samples were obtained from 33 patients with active plaque-type psoriasis before and after 12 weeks of therapy and from 11 healthy volunteers. Serum FABP4 concentrations were analyzed by the enzyme-linked immunosorbent assay (ELISA) and statistically analyzed for their correlations with clinical outcomes and the treatment introduced. Serum FABP4 levels were significantly increased in psoriatics compared to controls (p = 0.03). No relationship between the protein and psoriasis severity expressed through psoriasis area and severity index (PASI) was noted (p = 0.57). FABP4 did not correlate with CRP (p = 0.41), lipid profile, and body mass index (BMI) nor the glucose level or liver enzyme activity. FABP4 significantly correlated with morphotic blood elements. After total therapy, FABP4 did not statistically change (p = 0.07), but significantly decreased after administering acitretin (p = 0.03). FABP4 is a potential marker of psoriasis and clinical outcome after therapy with acitretin. Adipocyte-type FABP may be related to hematological disorders or obesity-mediated comorbidities in psoriasis.

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.

Liver fatty acid-binding protein might be a predictive marker of clinical response to systemic treatment in psoriasis

Fatty acid-binding proteins play an inconclusive role in lipid metabolism and cardiometabolic diseases (CMDs) which are closely related with psoriasis. Aim of the study was to investigate the diagnostic value of serum liver fatty acid-binding protein (FABP1) level and associations with disease severity, inflammation or metabolic parameters and influence of systemic treatment in psoriatic patients. The study included thirty-three patients with active plaque-type psoriasis and eleven healthy volunteers. Blood samples were obtained before and after 12 weeks of therapy with methotrexate and acitretin. Serum FABP1 concentrations were analyzed by the enzyme-linked immunosorbent assay. Statistical analysis was performed for correlation of FABP1 with anthropometric, metabolic or inflammatory indices and treatment used. Serum liver-type FABP levels were significantly increased in psoriatic patients compared to the controls (p < 0.001). No statistical correlations between FABP1 and PASI (p = 0.25) was noted, however patients with severe psoriasis had the highest level of FABP1. No significance with metabolic parameters was obtained, beside a positive significant relation with BMI after therapy (p = 0.03). Liver-type FABP significantly correlated with CRP (p = 0.01) and morphotic blood elements. Systemic treatment combined resulted in significant decrease of FABP1 (p = 0.04), regardless of the drug: p = 0.1 in acitretin group, p = 0.3 in methotrexate group. Liver-type FABP might be a novel marker of psoriasis and predictor of clinical response to systemic therapy. FABP1 could be involved in CMDs risk assessment and perhaps link psoriasis with hematological disorders.

Serum fatty acid binding protein 4 is positively associated with early stroke recurrence in nondiabetic ischemic stroke

Adipocyte fatty acid–binding protein (FABP4) played critical roles in metabolic syndrome, inflammatory responses and cardiovascular diseases. It aimed to investigate the associations of serum FABP4 levels with early stroke recurrence. This study included the 206 acute ischemic stroke patients hospitalized in our institution. Stroke recurrence events were assessed at the 3-month follow-up. The median of FABP level was 22.6 (IQR, 17.9-31.6) ng/mL in patients with stroke recurrence (N=36), which was higher than in patients without stroke recurrence [16.9 (IQR, 11.8-21.4) ng/mL] (P<0.001). As a continuous variable, the unadjusted and adjusted risk of stroke recurrence would be increased by 12% (OR=1.12 [95% CI 1.06–1.17], P<0.001) and 8% (1.08 [1.02–1.14], P=0.006) for every 1 ng/ml increment of FABP4. The Area under the curve (AUC) of serum FABP4 and NIH Stroke Scale (NIHSS) score for predicting stroke recurrence was 0.73 (95% CI: 0.64–0.82) and 0.72 (95% CI: 0.64–0.81), presenting no discriminating capacity (P=0.45). In the combining model, the AUC of NIHSS score was further improved to 0.77 by FABP4 (0.77; 95% CI: 0.69–0.85), which was significant (P=0.01). The risk of stroke recurrence can be predicted by elevated FABP4 levels in serum of nondiabetic patients with first-ever ischemic stroke.

High serum adipocyte fatty acid binding protein concentration linked with increased aortic arterial stiffness in patients with type 2 diabetes

BACKGROUND

Adipocyte fatty acid binding protein (A-FABP) is a novel adipokine that contributes to the development of metabolic disorder, type 2 diabetes mellitus (T2DM) and atherosclerosis. We determined the correlation between serum A-FABP and aortic stiffness in T2DM patients.

METHODS

Fasting blood samples were obtained from 156 patients with T2DM. Serum A-FABP concentration were determined using a commercial enzyme immunoassay. Carotid-femoral pulse wave velocity (cfPWV) was measured using SphygmoCor System, and cfPWV values of >10 m/s were defined as high aortic stiffness.

RESULTS

Sixty participants (38.4%) fell under the high aortic stiffness group. This group, compared to the control group, showed older age (P = .004), higher systolic blood pressure (P < .001), diastolic blood pressure (P = .027), urine albumin-to-creatinine ratio (P = .003), serum A-FABP (P < .001) and lower estimated glomerular filtration rate (P = .001). After adjusting for factors significantly associated with aortic stiffness using multivariable logistic regression analysis, serum A-FABP [OR = 1.029 (1.002-1.058), P = .039] was found to be an independent predictor of aortic stiffness in T2DM patients.

CONCLUSIONS

Serum A-FABP is positively correlated with aortic arterial stiffness in patients with T2DM.