Radiomics features based on dual-area CT predict the expression levels of fatty acid binding protein 4 and outcome in hepatocellular carcinoma

RATIONALE AND OBJECTIVES

To evaluate the predictive value of tumor and peritumor radiomics in the fatty acid binding protein 4 (FABP4) expression levels and overall survival in patients with hepatocellular carcinoma.

MATERIALS AND METHODS

The genomic data of HCC patients were obtained from The Cancer Genome Atlas. The Dual-area CT images of corresponding patients were downloaded from The Cancer Imaging Archive, for radiomics feature extraction, model construction and prognosis analysis. Simultaneously, using patients from Sichuan Provincial People's Hospital, the prognostic value of the radiomics model in HCC patients was validated.

RESULTS

In the TCIA database, the area under the curve (AUC) values of the volumes of interest (VOI)whole model in the training set and internal validation set were 0.812 and 0.754, respectively, and the AUC value of VOIwhole+periphery in the training set and internal validation set were 0.866 and 0.779, respectively. In the VOIwhole and the VOIwhole+periphery model of the independent cohort, there were significant differences in OS between the high and low rad-score groups (P = 0.009, P = 0.021, respectively). Significant positive correlations can be observed between FABP4 expression and correlations with rad-score of VOIwhole model (r = 0.691) and VOIwhole+periphery model (r = 0.732) in the independent cohort.

CONCLUSION

Radiomics models of tumor and peritumor Dual-area CT images could predict stably the expression levels of FABP4 and may be helping in personalized treatment strategies.

Integrated multi-omic analysis identifies fatty acid binding protein 4 as a biomarker and therapeutic target of ischemia-reperfusion injury in steatotic liver transplantation

BACKGROUND AND AIMS

Due to a lack of donor grafts, steatotic livers are used more often for liver transplantation (LT). However, steatotic donor livers are more sensitive to ischemia-reperfusion (IR) injury and have a worse prognosis after LT. Efforts to optimize steatotic liver grafts by identifying injury targets and interventions have become a hot issue.

METHODS

Mouse LT models were established, and 4D label-free proteome sequencing was performed for four groups: normal control (NC) SHAM, high-fat (HF) SHAM, NC LT, and HF LT to screen molecular targets for aggravating liver injury in steatotic LT. Expression detection of molecular targets was performed based on liver specimens from 110 donors to verify its impact on the overall survival of recipients. Pharmacological intervention using small-molecule inhibitors on an injury-related target was used to evaluate the therapeutic effect. Transcriptomics and metabolomics were performed to explore the regulatory network and further integrated bioinformatics analysis and multiplex immunofluorescence were adopted to assess the regulation of pathways and organelles.

RESULTS

HF LT group represented worse liver function compared with NC LT group, including more apoptotic hepatocytes (P < 0.01) and higher serum transaminase (P < 0.05). Proteomic results revealed that the mitochondrial membrane, endocytosis, and oxidative phosphorylation pathways were upregulated in HF LT group. Fatty acid binding protein 4 (FABP4) was identified as a hypoxia-inducible protein (fold change > 2 and P < 0.05) that sensitized mice to IR injury in steatotic LT. The overall survival of recipients using liver grafts with high expression of FABP4 was significantly worse than low expression of FABP4 (68.5 vs. 87.3%, P < 0.05). Adoption of FABP4 inhibitor could protect the steatotic liver from IR injury during transplantation, including reducing hepatocyte apoptosis, reducing serum transaminase (P < 0.05), and alleviating oxidative stress damage (P < 0.01). According to integrated transcriptomics and metabolomics analysis, cAMP signaling pathway was enriched following FABP4 inhibitor use. The activation of cAMP signaling pathway was validated. Microscopy and immunofluorescence staining results suggested that FABP4 inhibitors could regulate mitochondrial membrane homeostasis in steatotic LT.

CONCLUSIONS

FABP4 was identified as a hypoxia-inducible protein that sensitized steatotic liver grafts to IR injury. The FABP4 inhibitor, BMS-309403, could activate of cAMP signaling pathway thereby modulating mitochondrial membrane homeostasis, reducing oxidative stress injury in steatotic donors.

High-expression of FABP4 in Tubules is a Risk Factor for Poor Prognosis in DKD Patients

BACKGROUND

Lipid metabolism imbalance is involved in the mechanism of renal tubular injury in diabetic kidney disease (DKD). Fatty acid binding protein 4 (FABP4) has been reported to participate in cellular lipid toxicity. However, the expression of FABP4 in renal tissues of DKD and its correlation with clinical/ pathological parameters and prognosis have not been studied.

METHOD

A retrospective cohort study was conducted in 108 hospitalized Type 2 diabetes (T2D) patients with renal injury, including 70 with DKD and 38 with NDKD (non-DKD). Clinical features, pathological findings, and follow-up parameters were collected. Serum and urine FABP4 were detected by ELISA. An immunohistochemistry stain was used to determine FABP4 in renal tubulointerstitium. A double immunofluorescence stain was employed to assess FABP4- and CD68-positive macrophages. Correlation analysis, logistic regression models, receiver operating characteristic (ROC), and Kaplan-Meier survival curve were performed for statistical analysis.

RESULTS

DKD patients had increased expression of FABP4 and ectopic fat deposition in tubules. As shown by correlation analyses, FABP4 expression in renal tubules was positively correlated with UNAG (r=0.589, p=0.044) and ESRD (r=0.740, p=0.004). Multivariate regression analysis revealed that UNAG level was correlated with FABP4 expression level above median value (odds ratio:1.154, 95% confidence interval:1.009-1.321, p=0.037). High-expression of FABP4 in renal tubules of DKD was at an increased risk of ESRD. Increased FABP4 expression in inflammatory cells was also associated with ESRD in DKD.

CONCLUSION

High-expression of FABP4 is involved in the pathogenesis of renal tubular lipid injury and is a risk factor for poor prognosis in DKD patients.

Differential expressions of FASN, SCD, and FABP4 genes in the ribeye muscle of omega-3 oil-supplemented Tattykeel Australian White lambs

BACKGROUND

The concept of the functional nutritional value of health-beneficial omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) is becoming a phenomenon among red meat consumers globally. This study examined the expressions of three lipogenic genes (fatty acid binding protein 4, FABP4, fatty acid synthase, FASN; and stearoyl-CoA desaturase, SCD) in the ribeye (Longissimus thoracis et lumborum) muscle of Tattykeel Australian White (TAW) lambs fed fortified omega-3 diets and correlations with fatty acids. To answer the research question, "are there differences in the expression of lipogenic genes between control, MSM whole grain and omega-3 supplemented lambs?", we tested the hypothesis that fortification of lamb diets with omega-3 will lead to a down-regulation of lipogenic genes. Seventy-five six-month old TAW lambs were randomly allocated to the (1) omega-3 oil-fortified grain pellets, (2) unfortified grain pellets (control) or (3) unfortified MSM whole grain pellets diet supplements to generate three treatments of 25 lambs each. The feeding trial lasted 47 days.

RESULTS

From the Kruskal-Wallis test, the results showed a striking disparity in lipogenic gene expression between the three dietary treatments in which the FABP4 gene was significantly up-regulated by 3-folds in the muscles of lambs fed MSM Milling (MSM) whole grain diet compared to the omega-3 and control diets. A negative correlation was observed between FASN gene expression and intramuscular fat (IMF), eicosapentaenoic acid (EPA), total polyunsaturated fatty acids (PUFA), omega-6 polyunsaturated fatty acids (n-6 PUFA) and monounsaturated fatty acids (MUFA). The FABP4 gene expression was positively correlated (P < 0.05) with EPA and docosahexaenoic acid (DHA).

CONCLUSION

Taken together, this study's results suggest that FABP4 and FASN genes perform an important role in the biosynthesis of fatty acids in the ribeye muscle of TAW lambs, and supplementary diet composition is an important factor influencing their expressions.

Fatty acid binding protein 4 has prognostic value in peripheral artery disease

OBJECTIVE

Peripheral artery disease (PAD) remains undertreated, despite its association with major amputation and mortality. This is partly due to a lack of available disease biomarkers. The intracellular protein fatty acid binding protein 4 (FABP4) is implicated in diabetes, obesity, and metabolic syndrome. Given that these risk factors are strong contributors to vascular disease, we assessed the prognostic ability of FABP4 in predicting PAD-related adverse limb events.

METHODS

This was a prospective case-control study with 3 years of follow-up. Baseline serum FABP4 concentrations were measured in patients with PAD (n = 569) and without PAD (n = 279). The primary outcome was major adverse limb event (MALE; defined as a composite of vascular intervention or major amputation). The secondary outcome was worsening PAD status (drop in ankle-brachial index ≥0.15). Kaplan-Meier and Cox proportional hazards analyses adjusted for baseline characteristics were conducted to assess the ability of FABP4 to predict MALE and worsening PAD status.

RESULTS

Patients with PAD were older and more likely to have cardiovascular risk factors compared with those without PAD. Over the study period, MALE and worsening PAD status occurred in 162 (19%) and 92 (11%) patients, respectively. Higher FABP4 levels were significantly associated with 3-year MALE (unadjusted hazard ratio [HR], 1.19; 95% confidence interval [CI], 1.04-1.27; adjusted HR, 1.18; 95% CI, 1.03-1.27; P = .022) and worsening PAD status (unadjusted HR, 1.18; 95% CI, 1.13-1.31; adjusted HR, 1.17; 95% CI, 1.12-1.28; P < .001). Three-year Kaplan-Meier survival analysis demonstrated that patients with high FABP4 levels had a decreased freedom from MALE (75% vs 88%; log rank = 22.6; P < .001), vascular intervention (77% vs 89%; log rank = 20.8; P < .001), and worsening PAD status (87% vs 91%; log rank = 6.16; P = .013).

CONCLUSIONS

Individuals with higher serum concentrations of FABP4 are more likely to develop PAD-related adverse limb events. FABP4 has prognostic value in risk-stratifying patients for further vascular evaluation and management.

Identification of Andrographolide as a novel FABP4 inhibitor for osteoarthritis treatment

BACKGROUND AND PURPOSE

Fatty acid binding protein 4 (FABP4) has been identified as a contributor to cartilage degradation in osteoarthritis (OA) patients, and inhibiting FABP4 using small molecules has emerged as a promising approach for developing OA drugs. Our previous research showed that Andrographis paniculata, a medicinal plant, strongly inhibits FABP4 activity. This led us to hypothesize that Andrographis paniculata ingredients might have protective effects on OA cartilage through FABP4 inhibition.

METHODS

We analyzed scRNA-seq data from joint tissue of OA patients (GSE152805; GSE145286) using Scanpy 1.9.1 and Single Cell Portal. We conducted docking analysis of FABP4 inhibitors using Autodock Vina v.1.0.2. We evaluated the anti-FABP4 activity using a fluorescence displacement assay and measured the fatty acid oxidation (FAO) activity using the FAOBlue assay. We used H₂DCF-DA to measure reactive oxygen species (ROS) levels. We studied signaling pathways using bulk RNA sequencing and western blot analysis in human C28/I2 chondrocytes. We evaluated anti-OA activity in monosodium iodoacetate (MIA)-induced rats.

RESULTS

We identified Andrographolide (AP) as a novel FABP4 inhibitor. Bulk RNA-sequencing analysis revealed that FABP4 upregulated FAO and ROS in chondrocytes, which was inhibited by AP. ROS generation activated the NF-κB pathway, leading to overexpression of a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4), which is a responsible factor for cartilage degradation in OA patients. AP inhibited FABP4, thereby reducing the overexpression of ADAMTS4 by inhibiting the NF-κB pathway. In MIA rats, AP treatment reduced the overexpression of ADAMTS4, repaired cartilage and subchondral bone, and promoted cartilage regeneration.

CONCLUSION

Our results indicate that the inhibition of FABP4 activity by AP explains the anti-OA properties of Andrographis paniculata by protecting against cartilage degradation in OA patients. Additionally, our findings suggest that AP may be a promising therapeutic agent for OA treatment due to its ability to alleviate cartilage damage and bone erosion.

Fabkin and glucose homeostasis

BACKGROUND AND AIMS

The pathophysiology of different types of diabetes is incompletely understood. Fatty acid binding protein 4 (FABP4), an intracellular lipid chaperone, is secreted from adipocytes (during lipolysis) and macrophage. FABP4 is known to be associated with insulin resistance. However its precise role in the pathogenesis of T2DM is unclear. Fabkin, the hormonal complex of FABP4 with ADK (Adenosine Kinase) and NDPK (Nucleoside Diphosphate Kinase) is suggested to fill this gap in understanding pathogenesis. Herein, we summarize the role Fabkin in glucose homeostasis.

METHODS

Published relevant manuscripts that discussed the effect of FABP4 and Fabkin on glucose homeostasis were reviewed.

RESULTS

The formation of Fabkin complex is driven by the strong affinities of FABP4 to ADK and to inherent high-affinity interaction of ADK with NDPK. It does not have any definite receptors. The complex acts through the following pathways: i) by modulation of Glucose-Stimulated Insulin Signalling (GSIS) through extracellular ADP/ATP interaction via G-protein-coupled purinergic P2Y₁ receptors in pancreatic β-cells which are potently agonized by ADP and antagonized by ATP. Fabkin drives ADK to produce ATP, coupled with reduced generation of ADP. This results in low extracellular ADP/ATP ratio which leads to impairment of insulin secretion, ii) by regulating intracellular calcium dynamics iii) by producing Endoplasmic Reticulum (ER) stress.

CONCLUSIONS

Fabkin may integrate energy balance with functions of metabolic organs and thus play a major role in glucose homeostasis.

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.

Fatty acid binding protein 4 regulates pancreatic cancer cell proliferation via activation of nuclear factor E2-related factor 2

BACKGROUND

Obesity and diabetes are associated with an increased incidence of pancreatic cancer. Fatty acid binding protein 4 (FABP4), noted to be higher in patients with severe obesity, is linked to the development and progression of several cancers, and its level in the circulation decreases after bariatric surgery.

OBJECTIVE

In this paper, we evaluate the role of FABP4 in pancreatic cancer progression.

SETTING

University Hospital and Laboratories, United States.

METHODS AND RESULTS

When Panc-1 (human) and Pan02 (mouse) pancreatic cancer cells were treated with FABP4 or the-single-point mutant FABP4 (R126Q, fatty acid binding site mutant), only FABP4 stimulated cellular proliferation. The transcriptional activity of nuclear factor E2-related factor 2 (NRF2) was increased in response to FABP4 but not the R126Q. FABP4 treatment also led to downregulation of reactive oxygen species (ROS) activity. Consistent with induced cell propagation by FABP4, the growth of Pan02 tumor was decreased in FABP4-null animals compared with C57BL/6J controls.

CONCLUSION

These results suggest that FABP4 increases pancreatic cancer proliferation via activation of NRF2 and downregulation of ROS activity.

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.

Fatty acid binding protein-4 promotes alcohol-dependent hepatosteatosis and hepatocellular carcinoma progression

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Fatty liver disease (hepatosteatosis) is a hallmark of ALD and NAFLD.

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FABP4 is normally expressed in adipocytes and macrophages.

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ALD leads to FABP4 synthesis/release from steatotic hepatocytes.

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FABP4 stimulates hepatoma cell growth and migration.

Fatty liver disease (hepatosteatosis) is a common early pathology in alcohol-dependent and obese patients. Fatty acid binding protein-4 (FABP4) is normally expressed in adipocytes and macrophages and functions as a regulator of intracellular lipid movement/storage. This study sought to investigate hepatic FABP4 expression and function in alcoholic liver disease (ALD) and hepatocellular carcinoma (HCC). Using chronic ethanol fed mouse models and patient samples FABP4 expression was analyzed. Human HCC cells, and HCC cells transfected to express CYP2E1, were exposed to ethanol and analyzed for FABP4 expression, or exposed to rhFABP4 (in the absence/presence of ERK, p38-MAPK or JNK1/2 inhibitors) and cell proliferation and migration measured. Hepatosteatotic-ALD mouse models exhibited increased hepatic FABP4 mRNA and protein levels, with FABP4 expression confirmed in hepatocytes. In HCC cells, CYP2E1-dependent ethanol metabolism induced FABP4 expression in vitro and exogenous rhFABP4 stimulated proliferation and migration, effects abrogated by ERK and JNK1/2 inhibition. Increased FABP4 was also detected in ALD/ALD-HCC patients, but not patients with viral hepatitis/HCC. Collectively these data demonstrate ethanol metabolism induces hepatic FABP4 expression and FABP4 promotes hepatoma cell proliferation/migration. These data suggest liver-derived FABP4 may be an important paracrine-endocrine factor during hepatic foci expansion and/or hepatoma progression in the underlying setting of ALD.

FABP4 promotes invasion and metastasis of colon cancer by regulating fatty acid transport

Background

The prognosis of colon cancer is poor for metastasis, while the mechanism, especially adipocytes related, is not yet clear. The purpose of this study is to determine the effects of fatty acid binding protein 4 (FABP4), a transporter for lipids, on colon cancer progression.

Methods

The distribution of lipids and FABP4 was tested in the colon cancer tissues and adjacent normal tissues, and their relationship was also verified in vitro. Experiments about cellular invasion, migration and proliferation were performed to detect the impacts of FABP4 on the biological behaviors of colon cancer, and the positive results were checked in vivo. Meanwhile, the regulatory role of FABP4 in the energy and lipid metabolism was evaluated by the levels of triglyceride, ATP, LDH, glycerol and NEFA. At last, GO and KEGG analysis based on FABP4 overexpressed cells was performed, and the AKT pathway and epithelial-mesenchymal transition (EMT)-related proteins were determined by Western blot.

Results

Higher accumulation of lipids and stronger FABP4 transcription were observed in colon cancer tissues. Having been incubated with adipose tissue extract and overexpressed FABP4, colon cancer cells demonstrated enhanced lipid accumulation. In functional experiments, co-culture with adipose tissue extract significantly enhanced the invasion and migration of colon cancer cells, as well as the energy and lipid metabolism, and all these processes were reversed by FABP4 inhibitor. In addition, the metastasis of FABP4-overexpressed colon cancer cells was also significantly enhanced in vitro and in vivo. In terms of mechanism, the bioinformatics analysis showed that FABP4 was enriched in 11 pathways related to metabolic processes in FABP4 overexpressed cells. Finally, FABP4 overexpression improved EMT progression of colon cancer, as evidenced by the upregulation of Snail, MMP-2 and MMP-9, the downregulation of E-cadherin. The expression of p-Akt was also elevated.

Conclusion

FABP4 overexpression could increase FAs transport to enhance energy and lipid metabolism, and activate AKT pathway and EMT to promote the migration and invasion of colon cancer cells.

A FABP4-PPARγ signaling axis regulates human monocyte responses to electrophilic fatty acid nitroalkenes

Nitro-fatty acids (NO2-FA) are electrophilic lipid mediators derived from unsaturated fatty acid nitration. These species are produced endogenously by metabolic and inflammatory reactions and mediate anti-oxidative and anti-inflammatory responses. NO2-FA have been postulated as partial agonists of the Peroxisome Proliferator-Activated Receptor gamma (PPARγ), which is predominantly expressed in adipocytes and myeloid cells. Herein, we explored molecular and cellular events associated with PPARγ activation by NO2-FA in monocytes and macrophages. NO2-FA induced the expression of two PPARγ reporter genes, Fatty Acid Binding Protein 4 (FABP4) and the scavenger receptor CD36, at early stages of monocyte differentiation into macrophages. These responses were inhibited by the specific PPARγ inhibitor GW9662. Attenuated NO2-FA effects on PPARγ signaling were observed once cells were differentiated into macrophages, with a significant but lower FABP4 upregulation, and no induction of CD36. Using in vitro and in silico approaches, we demonstrated that NO2-FA bind to FABP4. Furthermore, the inhibition of monocyte FA binding by FABP4 diminished NO2-FA-induced upregulation of reporter genes that are transcriptionally regulated by PPARγ, Keap1/Nrf2 and HSF1, indicating that FABP4 inhibition mitigates NO2-FA signaling actions. Overall, our results affirm that NO2-FA activate PPARγ in monocytes and upregulate FABP4 expression, thus promoting a positive amplification loop for the downstream signaling actions of this mediator.

Dietary fatty acid content influences the expression of genes involved in the lipid turnover and inflammation in mouse colon and spleen

BACKGROUND

Dietary interventions can improve gastrointestinal (GI) symptoms. We determined the effects of fatty acids (FAs) supplementation with medium- and long-chain saturated FAs on mouse GI motility and correlated them with the expression of genes for free FA receptors (FFAR)1-4, FA binding protein 4 (FABP4) and inflammation.

METHODS

Forty-eight BalbC were assigned to: standard diet (STD), diet rich in medium-chain saturated FAs (COCO) and long-chain saturated FAs (HF) (7% by weight). Body weight (BW) and food intake (FI) were monitored for 8-weeks. GI motility was determined by fecal pellet output (FPO) and colon bead expulsion tests. FABP4 inhibitor, BMS309403 (1mg/kg, ip) was injected to half of each group 2 days/week. mRNA expression of FABP4, (FFAR)1-4, and pro-inflammatory cytokines were measured in colonic and splenic tissues using real-time PCR.

RESULTS

COCO and HF decreased FI. COCO accelerated overall GI transit (p<0.05). COCO increased the mRNA expression of FFAR2 (p<0.001) and TNFα (p<0.01); HF increased the expression of FABP4 and FFAR4 (p<0.05), and FFAR2 (p<0.001) in the colon, and decreased FFAR1 and FFAR4 (p<0.001), TNFα (p<0.01) and IL-1β (p<0.05) in splenic tissues. BMS309403 decreased the FI and delayed colonic transit in STD+BMS and COCO+BMS vs. STD (p<0.05). HF+BMS increased colonic expression of FFAR3 (p<0.01), TNFα (p<0.01), IL-6 (p<0.01), and reduced FFAR4 (p<0.05); COCO+BMS decreased TNFα (p<0.01).

CONCLUSION

Diversification in the dietary lipid content affected GI motility in mice and the expression of FFARs and pro-inflammatory cytokines in vivo.

Chain length of dietary fatty acids determines gastrointestinal motility and visceromotor function in mice in a fatty acid binding protein 4-dependent manner

Purpose

We hypothesize that different types of dietary fatty acids (FAs) affect gastrointestinal (GI) motility and visceromotor function and that this effect can be regulated by the fatty acid binding protein 4 (FABP4).

Methods

Mice were fed for 60 days with standard diet (STD), STD with 7% (by weight) coconut oil, rich in medium-chain FAs (MCFAs) (COCO), or with 7% evening primrose oil, rich in long-chain FAs (LCFAs) (EPO). In each group, half of the mice received FABP4 inhibitor, BMS309403 (1 mg/kg; i.p.) twice a week. Body weight (BW) and food intake were measured; well-established tests were performed to characterize the changes in GI motility and visceral pain. White adipose tissue and colonic samples were collected for cell culturing and molecular studies.

Results

COCO significantly increased GI transit, but not colonic motility. COCO and EPO delayed the onset of diarrhea, but none affected the effect of loperamide. EPO reduced BW and increased the visceromotor response (VMR) to colorectal distension (CRD). COCO and EPO reduced differentiation of preadipocytes. Treatment with BMS309403: (1) reversed the effects induced by COCO in physiological conditions and in mouse models of diarrhea; (2) prevented the effects of EPO on BW, VMR to CRD and castor oil-induced diarrhea; (3) affected proliferation of preadipocytes; (4) changed the expression of Fabp4 in colonic and adipocyte samples from COCO and EPO.

Conclusion

Modifying dietary intake of MCFAs and LCFAs may be used to control GI motility or visceral pain and thus modulate the symptoms of functional GI disorders. The effect is dependent on the expression of FABP4.

Electronic supplementary material

The online version of this article (10.1007/s00394-019-02094-2) contains supplementary material, which is available to authorized users.

Decreased serum fatty acid binding protein 4 concentrations are associated with sarcopenia in chronic hemodialysis patients

BACKGROUND

Fatty acid binding protein 4 (FABP4) is found to play a role in skeletal muscle homeostasis. Since the dysregulation of FABP4 and sarcopenia are both highly prevalent in patients on chronic hemodialysis (HD), the correlation between them remains unknown. We aimed to examine this relationship in a cross-sectional study.

METHODS

A total of 120 chronic HD patients were recruited, and whose skeletal muscle mass, handgrip strength, and gait speed were assessed and blood samples were obtained. We grouped these participants into sarcopenia (n = 20) and non-sarcopenia groups according to European Working Group on Sarcopenia in Older People criteria.

RESULTS

The sarcopenia group exhibited lower weight (P < 0.001), height (P = 0.019), waist circumference (P < 0.001), body mass index (P < 0.001), body fat mass (P = 0.004), and lower serum triglycerides (P = 0.009), creatinine (P < 0.001), phosphorus (P = 0.013), intact parathyroid hormone (P = 0.012), and FABP4 concentrations (P = 0.005), and higher malnutrition-inflammation scores (MIS) (P = 0.031), urea reduction rates (P < 0.001), and fractional clearance index for urea (Kt/V) values (P < 0.001). Serum FABP4 concentrations (odds ratio (OR): 0.98, 95% confidence interval (CI): 0.96-0.99, P = 0.043), body fat mass (OR: 0.86, 95% CI: 0.77-0.97, P = 0.013), MIS (OR: 6.90, 95% CI: 1.31-36.36, P = 0.023), and Kt/V (each increase of 0.1, OR: 2.15, 95% CI: 1.29-3.57, P = 0.003) were independent predictors of sarcopenia in chronic HD patients.

CONCLUSIONS

We delineated the association between serum FABP4 concentrations and sarcopenia in chronic HD patients.

Knocking out or pharmaceutical inhibition of fatty acid binding protein 4 (FABP4) alleviates osteoarthritis induced by high-fat diet in mice

OBJECTIVES

Adipokines play roles in the pathogenesis of osteoarthritis (OA). Fatty acid binding protein 4 (FABP4) is a novel adipokine that is closely associated with obesity and metabolic diseases. The aim of this study was to discover the potential role of FABP4 in OA.

METHODS

Seventy-two FABP4 knockout mice (KO) in C57BL/6N background and wild-type littermates (WT) (male, 6-week-old) were fed with a high-fat diet (HFD, 60% calorie) or standard diet (STD, 11.6% calorie) for 3 months, 6 months and 9 months (n = 6 each). In the parallel study, forty-eight 6-week-old male WT mice were fed with HFD or STD, and simultaneously treated with daily oral gavage of selective FABP4 inhibitor BMS309403 (15 mg/kg/d) or vehicle for 4 months and 6 months (n = 6 each). Serum FABP4 and cartilage oligomeric matrix protein (COMP) concentration was quantified. Histological assessment of knee OA and micro-CT analysis of subchondral bone were performed.

RESULTS

HFD induced obesity in mice. After 3 months and 6 months of HFD, KO mice showed alleviated cartilage degradation and synovitis, with significantly lower COMP, modified Mankin OA score, and MMP-13/ADAMTS4 expression. After 6 months and 9 months of HFD, KO mice showed less osteophyte formation and subchondral bone sclerosis. Chronic treatment of BMS309403 for 4 months and 6 months significantly alleviated cartilage degradation, but had no effects on the subchondral bone. Knocking out or pharmaceutical inhibition of FABP4 did not have significant effects on lean mice fed with STD.

CONCLUSIONS

Knocking out or pharmaceutical inhibition of FABP4 alleviates OA induced by HFD in mice.

FABP4 induces asthmatic airway epithelial barrier dysfunction via ROS-activated FoxM1

Functional abnormal airway epithelial cells, along with activated inflammatory cells, resulting in chronic airway inflammation, are considered as the characteristic of asthma. Fatty Acid Binding Protein 4 (FABP4) takes part in glucose and lipid homeostasis, and also have an important role in allergic airway inflammation. However, whether FABP4 influence barrier function of airway epithelial cells is unknown. In vivo, a HDM-induced murine model of asthma was obtained to assessed airway inflammation and protein expression of E-cadherin and Forkhead Box M1 (FoxM1). In vitro, 16-HBE was cultured and was treated with hrFABP4, siFABP4, FABPF4 inhibitor BMS, or FoxM1 inhibitor RCM-1. IL-4, IL-5, and IL-13 level was determined by ELISA. Transepithelial electrical resistance (TER), paracellular permeability and E-cadherin-special immunofluorescence were measured to value airway epithelial barrier function. Intracellular ROS production was determined by DCF-DA fluorescence. FABP4 inhibitor BMS alleviate airway inflammation and destruction of E-cad in allergic mouse. Treatment with HDM or hrFABP4 aggravated inflammatory response, damaged airway epithelial barrier, which could be inhibited by siFABP4 and BMS. Treatment with HDM or hrFABP4 also enhanced levels of FoxM1, and Inhibited FoxM1 suppressed HDM- and hrFABP4-induced inflammation and airway epithelial barrier dysfunction. In addition, H₂O₂ promoted FoxM1 expression, HDM and hrFABP4 induced-FoxM1 could be inhibited by NAC, leading to decreased inflammation and improved airway epithelial barrier. Upregulated ROS induced by FABP4 was of significance in activating FoxM1 leading to airway inflammation and epithelial barrier dysfunction.

Fatty acid-binding protein 4 regulates fatty infiltration after rotator cuff tear by hypoxia-inducible factor 1 in mice

BACKGROUND

Fatty infiltration in skeletal muscle is directly linked to loss of muscle strength and is associated with various adverse physical outcomes such as muscle atrophy, inflammation, insulin resistance, mobility impairments, and even mortality in the elderly. Aging, mechanical unloading, muscle injury, and hormonal imbalance are main causes of muscle fat accumulation, and the fat cells are derived from muscle stem cells via adipogenic differentiation. However, the pathogenesis and molecular mechanisms of fatty infiltration in muscles are still not fully defined. Fatty acid-binding protein 4 (FABP4) is a carrier protein for fatty acids and is involved in fatty acid uptake, transport, and lipid metabolism. Rotator cuff tear (RCT) usually occurs in the elderly and is closely related with fatty infiltration in injured muscle. To investigate potential mechanisms for fatty infiltration other than adipogenic differentiation of muscle stem cells, we examined the role of FABP4 in muscle fatty infiltration in an RCT mouse model.

METHODS

In the RCT model, we evaluated the expression of FABP4 by qRT-PCR, western blotting, and immunohistochemical analyses. Histological changes such as inflammation and fat accumulation in the injured muscles were examined immunohistochemically. To evaluate whether hypoxia induces FABP4 expression, the levels of FABP4 mRNA and protein in C3H10T1/2 cells after hypoxia were examined. Using a transient transfection assay in 293T cells, we assessed the promoter activity of FABP4 by hypoxia-inducible factors (HIFs). Additionally, we evaluated the reduction in FABP4 expression and fat accumulation using specific inhibitors for HIF1 and FABP4, respectively.

RESULTS

FABP4 expression was significantly increased after RCT in mice, and its expression was localized in the intramuscular fatty region. Rotator cuff tear-induced FABP4 expression was up-regulated by hypoxia. HIF1α, which is activated by hypoxia, augmented the promoter activity of FABP4, together with HIF1β. Hypoxia-induced FABP4 expression was significantly decreased by HIF1 inhibitor treatment. Furthermore, in RCT model mice, fat accumulation was remarkably reduced by FABP4 inhibitor treatment.

CONCLUSIONS

This study shows that RCT induces FABP4 expression, leading to fat accumulation in injured muscle. FABP4 transcription is regulated by the direct binding of HIF1 to the FABP4 promoter in the hypoxic condition induced by RCT. Fat accumulation in injured muscle was reduced by the inhibition of FABP4. Ultimately, in the RCT model, we identified a novel mechanism for fatty infiltration by FABP4, which differs from adipogenic differentiation of muscle stem cells, and we found that fatty infiltration might be regulated by inhibition of HIF1 or FABP4.

Prognostic Utility of Fatty Acid-Binding Protein 4 in Patients with Type 2 Diabetes and Acute Ischemic Stroke

The role of fatty acid-binding proteins (FABPs) in atherosclerosis has been investigated. The aim of this study was to verify the hypothesis that higher levels of serum fatty acid-binding protein 4 (FABP4) could be a prognostic factor in Chinese patients with type 2 diabetes (T2DM) and acute ischemic stroke (AIS). From September 2015 to August 2016, consecutive first-ever AIS patients combined with T2DM were included in this study. FABP4, NIH stroke scale (NIHSS), and conventional risk factors were evaluated to determine their value to predict functional outcomes within 3 months. Multivariate analyses were performed using logistic regression models. We measured FABP4 in 329 patients. The median age of patients included in this study was 63 (IQR, 56-72) years and 45.9% were women. FABP4 serum levels were obtained at a median of 8.5 h (IQR, 4.0-14.0 h) after the stroke onset with a median value of 21.4 ng/ml (IQR, 15.6-28.2 ng/ml). In multivariable models, FABP4 remained an independent stroke severity predictor with an adjusted OR of 1.05 (95% CI, 1.02-1.09). In multivariate models comparing the third (odd ratio (OR), 2.25; 95% confidence interval (CI), 1.59-3.54) and fourth quartiles (OR, 3.75; 95% CI, 2.48-5.03) against the first quartile of the FABP4, levels of FABP4 were associated with poor functional outcome. At 3 months, 38 patients (11.6%; 95%CI, 8.1-15.0%) had died. The mortality distribution across the FABP4 quartiles ranged between 3.7% (first quartile) and 20.7% (fourth quartile). Elevation of FABP4 is associated with an increased risk of death and poor functional outcome events in patients with type 2 diabetes and acute ischemic stroke and is independent of other established clinical risk predictors and biomarkers.

Fatty acid binding protein 4 is associated with stroke risk and severity in patients with acute ischemic stroke

OBJECTIVE

The role of fatty acid-binding proteins (FABPs) in atherosclerosis has been investigated. The aim of this study was to verify the hypothesis that higher levels of serum FABP4 could be a biomarker for stroke and associated with stroke severity in Chinese patients with ischemic stroke.

METHODS

All consecutive patients with first-ever acute ischemic stroke from September 2015 to August 2016 were recruited to participate in the study. Serum FABP4 levels and routine tests were examined at admission. The National Institutes of Health Stroke Scale (NIHSS) score was assessed on admission blinded to FABP4 levels.

RESULTS

We recorded 277 stroke patients. There was a significant difference in median serum FABP4 levels between stroke patients and control cases (P<0.001). Serum FABP4 levels increased with increasing severity of stroke as defined by the NIHSS score. The result illustrates the time course of serum FABP4, showing significant changes with day of sampling, with peak levels on day 1, falling to a plateau by days 2 to 5. At admission, 129 patients (46.6%) had a minor stroke (NIHSS≤5). In these patients, the median serum FABP4 level was lower than that observed in patients with moderate-to-sever clinical severity (P<0.001). In multivariate models comparing the second, third, and fourth quartiles against the first quartile of the FABP4, levels of FABP4 were associated with stroke risk and severity.

CONCLUSION

High levels of FABP4 are significantly related to stroke risk and severity, independent from other traditional and emerging risk factors, suggesting that they may play a role in stroke pathogenesis.

Increased expression of fatty acid binding protein 4 in preeclamptic Placenta and its relevance to preeclampsia

The aim of this investigation was to determine the expression of fatty acid binding protein 4 (FABP4) in the placenta from women with preeclampsia and normal pregnancy, and to delineate the regulatory effects on thophoblast cell by FABP4. We determined the expression of FABP4 by real-time polymerase chain reaction (PCR) for messenger ribonucleic acid (mRNA) or enzyme-linked immunesorbent assay (ELISA) and Western blotting for protein. Small interference of ribonucleic acid (siRNA) and specific FABP4 inhibitor were used to inhibit FABP4. The proliferation, migration and invasion of trophoblastic cells (Swan-71 and Jar) were evaluated with cell counting kit-8, wound-healing test and transwell analysis respectively. We found the expression of FABP4 was significantly higher in the placenta of preeclamptic women than that of women with normal pregnancy (t = 4.244, P < 0.001 for mRNA; t = 4.536, P < 0.001 for protein). FABP4 siRNA significantly reduced the proliferation of trophoblasts (P < 0.001). The specific inhibition of FABP4 inhibited the proliferation of trophoblasts in a dose-dependent manner (P < 0.001) and the inhibitory effect increased as the concentration of inhibitor increased. FABP4 siRNA and specific inhibitor significantly decreased the migration (P < 0.001) and invasion (P < 0.001) of trophoblasts. We concluded the increase in placental FABP4 expression in preeclampsia may affect the function of trophoblast, and this increase may have a role in the pathogenesis of preeclampsia.

High ω-3:ω-6 fatty acids ratio increases fatty acid binding protein 4 and extracellular secretory phospholipase A2IIa in human ectopic endometrial cells

BACKGROUND

Endometriosis, a common chronic inflammatory disorder, is defined by the atypical growth of endometrium- like tissue outside of the uterus. Secretory phospholipase A2 group IIa (sPLA2-IIa) and fatty acid binding protein4 (FABP4) play several important roles in the inflammatory diseases.

OBJECTIVE

Due to reported potential anti-inflammatory effects of ω-3 and ω-6 fatty acids, the purpose of the present study was to investigate the effects of ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) on fatty acid binding protein 4 and extracellular secretory phospholipase A2IIa in cultured endometrial cells.

MATERIALS AND METHODS

Ectopic and eutopic endometrial tissues obtained from 15 women were snap frozen. After thawing and tissue digestion, primary mixed stromal and endometrial epithelial cell culture was performed for 8 days in culture mediums supplemented with normal and high ratios of ω-3 and ω-6 PUFA. sPLA2-IIa in the culture medium and FABP4 level was determined using enzyme immuno assay (EIA) technique.

RESULTS

Within ectopic endometrial cells group, the level of cellular FABP4 and extracellular sPLA2-IIa were remarkably increased under high ω-3 PUFA exposure compared with control condition (p=0.014 and p=0.04 respectively).

CONCLUSION

ω-3 PUFAs may increase the level of cellular FABP4 and extracellular sPLA2-IIa in ectopic endometrial cells, since sPLAIIa and FABP4 may affect endometriosis via several mechanisms, more relevant studies are encouraged to know the potential effect of increased cellular FABP4 and extracellular sPLA2-IIa on endometriosis.

Radiofluorinated probe for PET imaging of fatty acid binding protein 4 in cancer

INTRODUCTION

Cancer-associated adipocytes metabolically interact with adjacent cancer cells to promote tumor proliferation and metastasis. Fatty acid binding protein 4 (FABP4) participates in this interaction, and is gathering attention as a therapeutic and diagnostic target. Positron emission tomography (PET) is a useful diagnostic method that enables noninvasive in vivo quantitative imaging of biofunctional molecules with probes labeled with positron-emitting radioisotopes. Here a novel (18)F labeled probe for PET FABP4 imaging developed through dedicated drug design from a radioiodinated probe we recently reported is evaluated in vitro and in vivo.

METHODS

We designed the [(18)F]-labeled FTAP1 and FTAP3 probe, composed of a single or triple oxyethylene linker and a triazolopyrimidine scaffold derived from an FABP4 inhibitor. FABP4 binding affinities for chemically synthesized FTAP1 and FTAP3 were measured using FABP4 and 8-anilino-1-naphthalene sulfonic acid. Cell membrane permeability was measured using a commercially available plate assay system. After radiosynthesis, [(18)F]FTAP1 affinity and selectivity were evaluated using immobilized FABP3, FABP4, and FABP5. Cell uptake was investigated using differentiated adipocytes expressing FABP4 with inhibitor treatment. Following biodistribution studies in C6 glioblastoma-bearing mice, ex vivo autoradiography and immunohistochemistry were performed using thin sliced tumor sections. PET/CT imaging was then performed on C6 tumor bearing mice.

RESULTS

FTAP1 showed high FABP4 affinity (Ki=68±8.9 nM) and adequate cell permeability. [(18)F]FTAP1 with ≥98% radiochemical purity was shown to selectively bind to FABP4 (16.3- and 9.3-fold higher than for FABP3 and FABP5, respectively). [(18)F]FTAP1 was taken up by FABP4 expressing cells, and this uptake could be blocked by an inhibitor, indicating very low non-specific cell binding. [(18)F]FTAP1 showed high tumor accumulation, which demonstrates its potential use for in vivo tumor PET imaging, and the intratumoral radioactivity distribution corresponded to the FABP4 expression profile.

CONCLUSION

[(18)F]FTAP1 is a promising PET probe to target FABP4.

Peri-conceptional obesogenic exposure induces sex-specific programming of disease susceptibilities in adult mouse offspring

Vulnerability of the fetus upon maternal obesity can potentially occur during all developmental phases. We aimed at elaborating longer-term health outcomes of fetal overnutrition during the earliest stages of development. We utilized Naval Medical Research Institute (NMRI) mice to induce pre-conceptional and gestational obesity and followed offspring outcomes in the absence of any postnatal obesogenic influences. Male adult offspring developed overweight, insulin resistance, hyperleptinemia, hyperuricemia and hepatic steatosis; all these features were not observed in females. Instead, they showed impaired fasting glucose and a reduced fat mass and adipocyte size. Influences of the interaction of maternal diet∗sex concerned offspring genes involved in fatty liver disease, lipid droplet size regulation and fat mass expansion. These data suggest that a peri-conceptional obesogenic exposure is sufficient to shape offspring gene expression patterns and health outcomes in a sex- and organ-specific manner, indicating varying developmental vulnerabilities between sexes towards metabolic disease in response to maternal overnutrition.

Peri-conceptional obesogenic exposure induces sex-specific programming of disease susceptibilities in adult mouse offspring

Vulnerability of the fetus upon maternal obesity can potentially occur during all developmental phases. We aimed at elaborating longer-term health outcomes of fetal overnutrition during the earliest stages of development. We utilized Naval Medical Research Institute (NMRI) mice to induce pre-conceptional and gestational obesity and followed offspring outcomes in the absence of any postnatal obesogenic influences. Male adult offspring developed overweight, insulin resistance, hyperleptinemia, hyperuricemia and hepatic steatosis; all these features were not observed in females. Instead, they showed impaired fasting glucose and a reduced fat mass and adipocyte size. Influences of the interaction of maternal diet∗sex concerned offspring genes involved in fatty liver disease, lipid droplet size regulation and fat mass expansion. These data suggest that a peri-conceptional obesogenic exposure is sufficient to shape offspring gene expression patterns and health outcomes in a sex- and organ-specific manner, indicating varying developmental vulnerabilities between sexes towards metabolic disease in response to maternal overnutrition.