Skip to main content
Download PDF

Resistin upregulates fatty acid oxidation in synoviocytes of metabolic syndrome-associated knee osteoarthritis via CAP1/PKA/CREB to promote inflammation and catabolism

Arthritis Research & Therapy volume 27, Article number: 99 (2025) Cite this article

Abstract

Background

Metabolic Syndrome (MetS), as a syndrome characterized by low-grade inflammation and energy metabolism disorders, is considered to be an important systemic risk factor for knee osteoarthritis (KOA). Our previous study showed that the protein level of serum resistin was positively correlated with the degree of metabolic disorder in MetS-OA. However, whether Resistin promotes the progression of KOA synovitis and the underlying mechanisms remain unclear. This study mainly investigateswhether there were metabolism disorder which promote inflammatory and catabolic phenotype in fibroblast-like synoviocytes (FLS) from KOA patients with MetS (MetS-KOA-FLS), and the roles and mechanisim of resistin in MetS-KOA-FLS.

Methods

Comparative analysis of synovium and FLS from MetS-associated KOA (MetS-KOA) and non-MetS-associated KOA (nMetS-KOA) of females to detect the differences in inflammation, catabolism and glycolipid metabolism. Serum from MetS-KOA stimulated nMetS-KOA-FLS to detect the effect of MetS microenvironment on inflammation, catabolism and glycolipid metabolism of nMetS-KOA-FLS. Resistin stimulated MetS-KOA-FLS to explore the effect of resistin on inflammation and catabolism of MetS-KOA-FLS and its specific mechanism.

Results

Compared with nMetS-KOA-FLS, MetS-KOA-FLS expressed higher inflammatory related factors, catabolic enzymes, and showed stronger adhesive and invasive ability. Resistin was found to be an important factor in the serum and internal environment of MetS-KOA patients, and it mediated the differences in fatty acid oxidation (FAO) between the two groups. Resistin activated the PKA/CREB pathway through CAP1 and upregulated FAO, promoting the inflammatory and catabolic phenotype of MetS-KOA-FLS.

Conclusions

This study clarifies the mechanism by which MetS causes synovitis from a metabolic perspective and provides new ideas for further research and treatment of MetS-KOA.

Introduction

Osteoarthritis (OA) is a chronic, degenerative musculoskeletal disease and a major cause of pain and disability in older adults [1]. In recent years, there has been growing research interest into how KOA is impacted by obesity, one of the few modifiable risk factors of OA [2]. Obesity not only causes high weight-induced stress and resulting injury on the knee joint, but also leads to abnormal energy metabolism, which seriously affects joint health. Therefore, metabolic syndrome-associated osteoarthritis (MetS-OA) has attracted the interest of many researchers [3].

Metabolic syndrome (MetS) is a constellation of metabolic abnormalities, and is accompanied by systemic low-grade inflammation [4]. An increasing number of studies have shown that MetS plays an important role in KOA progression, particularly in the Asian population. The effect of MetS on KOA was also shown to be more pronounced in women [5]. Therefore, in this study, the characteristics of female KOA patients with MetS will be investigated. As a systemic risk factor for OA, MetS has a particularly strong effect on the synovium, which has a rich blood supply. Indeed, a growing number of studies on the pathogenesis of OA support the important role of synovitis, which has a major impact on the degeneration of articular cartilage and OA progression [6, 7]. Fibroblast-like synovial cells (FLS) promote cell infiltration and angiogenesis by increasing the expression of pro-inflammatory factors, and FLS also provide matrix degrading enzymes to the articular chondrocytes which contribute to their eventual phenotypic loss [8].

It has been suggested that adipokines may serve as a bridge linking the mechanisms of MetS and KOA. Our previous results showed that the level of resistin correlated with the severity of MetS and inflammation in patients with KOA [9]. Resistin has also been reported to regulate energy metabolism, though only in a small number of studies [10,11,12,13,14]. Changes in energy metabolism may be related to the occurrence and development of inflammation, and studies have shown that changes in lipid metabolism may promote the progression of inflammation [15]. However, whether resistin can affect the inflammation and catabolism of FLS by regulating energy metabolism has not been studied.

In this study, we aimed to explore whether there were metabolism disorder which promote inflammatory and catabolic phenotype in FLS from KOA patients with MetS (MetS-KOA-FLS), and the roles and mechanisim of resistin in MetS-KOA-FLS. Our study will clarify the metabolic mechanism by which MetS causes synovitis, and provides new ideas for the future research and treatment of MetS-KOA.

Materials and methods

Collection of tissue samples

This study included 30 female KOA patients who underwent knee arthroplasty in the Department of Orthopaedic Surgery of the First Hospital of Jilin University from August 2020 to June 2021 and from September 2024 to December 2024. The inclusion criteria were as follows: (1) the diagnosis of KOA met the American College of Rheumatology’s diagnostic criteria for OA; (2) no drug use or drug test in the past month; (3) denied any history of knee trauma and surgery; (4) female patient. The exclusion criteria were as follows: (1) did not voluntarily sign the informed consent; (2) secondary KOA; (3) received intra-articular injection therapy within the past 6 months; (4) had a history of knee trauma or knee joint infection; (5) autoimmune diseases or diseases that affect other parts of the body, such as asthma, systemic lupus erythematosus, rheumatoid arthritis, and tumors. Those who met al.l 4 inclusion criteria and did not meet any one of the exclusion criteria were included in the study, and those who met any one of the 5 exclusion criteria were not included in the study. Female patients with KOA were divided into MetS-KOA and nMetS-KOA according to the NCEP-ATPIII criteria for the diagnosis of MetS in Asians [16], which gave 15 cases each of MetS-KOA and nMetS-KOA. The patients signed the informed consent form and we obtained consent for the study from the Medical Ethics Committee of the First Hospital of Jilin University (No. 2015 − 284). The patient tissue samples were then collected during the operation. Characteristics of the study population are shown in Supplementary Table S1.

After fasting for at least 8 h before surgery, 8 ml blood was collected. The samples were sent to the laboratory within 10 min, and centrifuged at 3000 rpm for 10 min at 4 °C. The serum was dispensed and numbered, and then stored in the − 80 °C freezer of the tissue specimen bank. During the total knee arthroplasty, the resected synovium of suprapatellar capsular was collected. The synovium used for pathological experiments was immediately fixed in a specimen bottle containing 10% neutral formalin. The synovium used for cell extraction was put into a sterile 15 ml tube, 10 ml of FBS-free DMEM high-glucose medium was added, and samples were quickly transferred to the laboratory within 20 min for cell extraction. The synovium was sent to the laboratory at 4 °C and then packed and numbered into the − 80 ℃ refrigerator of the tissue specimen bank for future use.

Isolation and culture of FLS

Isolation of FLS was done by enzymatic digestion [16]. The isolated synovium was washed three times with sterile PBS, and the synovium was cut into tissue fragments of approximately 2–3 mm3 in size. After washing, the synovium fragments were collected by centrifugation at 1500 rpm for 5 min, followed by addition of 2.5 mg/ml collagenase type I for digestion on a constant temperature shaker at 37 ℃ for 2 h. The digested solution was filtered, then centrifuged at 1500 rpm for 5 min. And the pellet was washed three times with PBS. The cell pellet was resuspended in high-glucose DMEM containing 10% FBS and 1% penicillin-streptomycin solution, transferred to a culture flask, and cultured in a 5% CO2 cell incubator at 37 ℃. The FLS used in this experiment were the 3rd to 6th generation.

Pathology experiments

The collected synovium was fixed in 10% neutral formalin, embedded in paraffin, sectioned, and stained with hematoxylin and eosin (H&E) and the relevant antibodies. Images were acquired under an OLYMPUS upright microscope using an Olympus D71 image acquisition system. At least 3 images were randomly taken for each tissue section, and statistical analysis was performed on the average level. The degree of synovitis was assessed according to the histopathological scoring criteria for synovitis [16]. The semi-quantitative assessment (ranging from 0 (absent) to 3 (intense)) was used based on three features of synovitis (proliferation of the synovial lining layer, cellular density of the synovial matrix, and leukocyte infiltration), each scored separately. The total score of synovitis was 0–1, with no synovitis; 2–4 points, low-grade synovitis; 5 to 9 points, high degree of synovitis. Antibodies used for immunohistochemistry were as follows: CAP1 (Abcam, ab155079), dilution ratio 1:200; ready-to-use HRP-polymer anti-rabbit IgG (MXB Biotechnologies, KIT-5920). ImageJ was used to measure the mean optical density.

Cell counting kit CCK-8

MetS-KOA-FLS were seeded on a 96-well plate at 5000 cells/well. The cells were cultured for 24 h to completely adhere, then various concentrations of resistin (0 ng/ml, 100 ng/ml, 200 ng/ml, 500 ng/ml) were added to the culture plate, with three replicate wells per condition. The 96-well plate was put back into the incubator, and 10 µl of CCK-8 solution was added to the wells at 6 h, 12 h, 24 h, 48 h, and 72 h, followed by further incubation for 1–4 h. The absorbance at 450 nm was measured with a microplate reader, and the cell viability was calculated.

Cell stimulation experiments

In the serum stimulation experiment, 1 ml of serum from 5 MetS patients were put into the same 15 ml centrifuge tube and mixed. nMetS-KOA-FLS were incubated for 24 h with DMEM containing 1% penicillin-streptomycin solution which was mixed with either the medium containing 5% MetS serum (serum stimulation group), or 5% FBS (control group).

In the pathway intervention experiment, 10 nM TAK-242 (MedChemExpress, HY-11109), 2.5 µM H-89 (Beyotime, S1643-1 mg), or 2.5 µM KG-501 (MedChemExpress, HY-103299) were pre-incubated with MetS-KOA-FLS for 1 h and then co-incubated with 200 ng/ml resistin for 24 h. For 2-Deoxy-D-glucose (2-DG) and Etomoxir (Eto) treatments, 10 mM 2-DG (Solarbio, D8930) or 100 µM Eto (Sigma, SIG-236020-5MG) were pre-incubated with MetS-KOA-FLS for 2 h and then 200 ng/ml resistin was added for a further 24 h.

Transfection

FLS were resuspended in high-glucose DMEM without penicillin-streptomycin solution, seeded in 12-well plates at 5 × 104 cells/well, and incubated for 24 h before transfection. The siRNA stock was diluted in high-glucose DMEM without penicillin-streptomycin solution to a final concentration of 50 nM for transfection. Lipofectamine 2000 (Invitrogen, 11668-019) was diluted in high-glucose DMEM without penicillin-streptomycin solution at a ratio of 1:50, and left to stand for 5 min at 25 ℃. The lipofectamine 2000 and siRNA diluents were mixed at a 1:1 ratio (100 µl each), gently pipetted 3–5 times, and left at 25 ℃ for 20 min. The medium in the 12-well plate containing cells was changed in advance, and 800 µl of high-glucose DMEM without penicillin-streptomycin solution was added to each well with 200 µl/well of the above transfection mixture. After 4–6 h of culture, the medium was replaced with fresh complete medium. Forty-eight hours after transfection, cells were treated with resistin and/or harvested for qPCR or WB to detect the silencing efficiency of siRNA at the gene or protein level. CAP1-siRNA was purchased from GENERAL BIOL in China, and the detailed sequence information is shown in Supplementary Table S2.

Western blotting and antibodies

The cells were washed twice with 4 °C pre-cooled PBS, then lysis on ice for 40 min. After ensuring complete cell lysis, the lysate was centrifuged at 12,000 rpm for 20 min at 4 °C and the supernatant was collected. Protein sample concentration was determined using a BCA kit (KeyGEN BioTECH, KGP902-500T). Loading buffer was added and mixed well with the sample, followed by centrifugation, and incubation in a water bath at 100 °C for 10 min. Approximately 20 µg per protein sample was added to 10% SDS-PAGE gel for electrophoresis to separate proteins. The resulting protein bands were transferred to nitrocellulose filter membrane. The blots were then incubated with primary antibody overnight at 4 ℃. Finally, fluorescent secondary antibody was added and incubated for 1 h, then developed and photographed in a Li-COR fluorescence imager. The gray value of the band was measured by AlphaEaseFC software, and statistical analysis was performed. Antibodies used were as follows: HK2 (Cell Signaling Technology, #2867), LDHA (Cell Signaling Technology, #3582), CPT1A (Cell Signaling Technology, #12252), CAP1 (Abcam, ab155079), TLR4 (WanleiBio, WL00196), CREB (Cell Signaling Technology, #9197), pCREBser133 (Cell Signaling Technology, #9198), β-actin (Cell Signaling Technology, #4970), Dylight 549, goat anti-rabbit IgG (Abbkine, ABB-A23320). The dilution ratio of primary antibody was 1:1000, and the dilution ratio of fluorescent secondary antibody was 1:10000.

Quantitative real-time polymerase chain reaction (qRT-PCR)

RNA was prepared using AG RNAex Pro RNA extraction reagent (ACCURATE BIOLOGY, AG21102). Reverse transcription PCR of RNA was performed using 5X All-In-One RT MasterMix cDNA Synthesis Kit (Applied Biological Material, G490). qPCR was performed on a Biorad CFX96 machine with the SYBR green-based program using the SYBR® Green Premix Pro Taq HS qPCR Kit (ACCURATE BIOLOGY, AG11701). Normalization was performed using the 2 −ΔΔCt method. PCR primers were designed using the online primer tool Primer3Plus. Detailed sequence information of primers is listed in Supplementary Table S3.

Invasion assay

Growth factor reduced (gfr) Matrigel (Becton, Dickinson and Company, 356231-10 ml, 8.9 mg/ml) was diluted 1:1 with DMEM. An 8.0 μm transwell chamber was coated with 30 µl of the diluted Matrigel and placed at 37 ℃ for 30 min. Next, serum-free cultured nMetS-KOA-FLS and MetS-KOA-FLS (2 × 104 cells per group) were seeded in transwell chambers (the method was the same for seeding cells with or without stimulation with resistin, 2-DG, and Eto). After 72 h of cell culture, the cells that did not pass through the filter membrane of the transwell chamber were wiped from the top surface with a cotton swab. The remaining cells on the bottom surface of the chamber were fixed in 4% (w/v) paraformaldehyde for 20 min, then stained with 0.1% (w/v) crystal violet and counted under the microscope. Invasion values were expressed as the mean number of migrating cells (200×) at the bottom of the chamber per 3 microscopic fields.

Adhesion assay

FLS were seeded in 20 mm glass bottom dishes at 1 × 105 cells/dish. After the cells were completely attached, they were treated according to the experimental plan, and collected by centrifugation at 3 × 105 cells/dish one hour before the end of the experimental treatment. BCECF AM was added to the THP-1 cell suspension to a final concentration of 10 µM. THP-1 cells were incubated in a 37 °C, 5% CO2 sterile cell incubator for 1 h in the dark, and then added to a culture dish at 3 × 105 cells/dish and incubated with FLS for 6 h. The unadherent THP-1 cells were removed by gentle washing with PBS 2–3 times, and images were taken on the OLYMPUS upright microscope using the Olympus D71 image acquisition system. Invasion values were expressed as the average number of adherent cells (100×) per microscope view at the bottom of the dish. Three fields of view were counted per dish. Adherent THP-1 cells were counted using ImageJ and the results were statistically analyzed using Graphpad.

ELISA

Debris or dead cells were removed from the cell culture supernatant by centrifugation, and then CCL3 (Nanjing Jiancheng Bioengineering Institute, H110), MMP13 (Nanjing Jiancheng Bioengineering Institute, H459-1), or ADAMTS4 (CUSABIO, CSB-E11848h) were detected in the cell culture supernatant according to the l instructions of the ELISA kit manufacturers.

Annexin V-FITC/7-AAD

1 × 105 cells per group were seeded in 12-well plates. In addition to the experimental group and the control group, 3 flow detection control groups (including the normal group, the 7-AAD single staining group, and the Annexin V-FITC single staining group) were set up to adjust the fluorescence compensation, remove spectral overlap, and set the position of the cross gate. After treatment, cells were digested with EDTA-free trypsin, and then collected by centrifugation at 1500 rpm for 5 min. The cells were washed by adding pre-cooled PBS buffer, and then centrifuged at 1500 rpm for 5 min to collect the cells, and washed again. The cells were resuspended in 100 µl of 1× Binding Buffer. Annexin V-FITC and 7-AAD (5 µl of each) were added to the experimental group and the control group, and the three flow cytometry control groups were prepared accordingly (normal cell group; no dye, 7-AAD single staining group; 5 µl of 7-AAD, Annexin V-FITC single staining group; 5 µl of Annexin V-FITC). After mixing, the samples were incubated at room temperature for 15 min in the dark. The flow cytometer NovoCyte Flow Cytometer (Agilent Technologies, CA, US) was used for detection, with FITC as the abscissa and 7-AAD as the ordinate to draw a two-color scatter plot.

Statistical analysis

Continuous variables were expressed as mean ± standard deviation (SD), and independent samples t-tests or paired t-tests were used for comparative analysis. The WB bands were measured by AlphaEaseFC software and converted into continuous variables for quantitative analysis, and then the differences between groups were compared. Experiments were independently repeated three times. P < 0.05 was considered statistically significant. All statistical analyses were performed using GraphPad Prism 7.0 software and Microsoft Excel.

Results

MetS-KOA shows more severer pathological inflammatory characteristics

We first compared pathological features of synovial tissue between MetS-KOA and non-MetS-associated KOA (nMetS-KOA) patients. We found that compared with nMetS-KOA, MetS-KOA displayed slightly thicker synovial lining cell layer and increased vascularity and inflammatory cell infiltration of the synovial membranes with the analysis of hematoxylin and eosin (H&E) staining (Fig. 1a). The results suggest that MetS-KOA patients may display more severer synovitis than nMetS-KOA patients.

Fig. 1
figure 1

Inflammation and catabolism are more active in synovial tissue and FLS in MetS-KOA than in nMetS-KOA. a H&E staining of synovial tissue from MetS-KOA and nMetS-KOA patients. Representative images are shown. The severity of synovitis was assessed using the histopathological scoring criteria for synovitis. n = 5. b In vitro mRNA levels of CCL2, CCL3, and CXCL8 and protein level of CCL3 in MetS-KOA-FLS relative to those in nMetS-KOA-FLS. c In vitro mRNA levels of adhesion factors ICAM1 and VCAM1 in MetS-KOA-FLS relative to those in nMetS-KOA-FLS. d In vitro mRNA levels of IL6 and TNFα of MetS-KOA-FLS relative to those in nMetS-KOA-FLS. e In vitro mRNA expression of VEGF and FGF2 of nMetS-KOA-FLS and MetS-KOA-FLS. f In vitro mRNA and protein levels of MMP13 and ADAMTS4 of nMetS-KOA-FLS and MetS-KOA-FLS. g Cell adhesion assays to detect the adhesion ability of FLS. Count of THP-1 cells after co-culture (3:1) with nMetS-KOA-FLS and MetS-KOA-FLS for 6 h. h Invasion assays to detect the invasion ability of FLS. Count of invasive nMetS-KOA-FLS or MetS-KOA-FLS cells. n = 5. All data are expressed as means ± s.e.m. Statistical significance is indicated as *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, as assessed by two-sided Student’s t-test

Full size image

Next we compared the FLS characteristics associated to inflammation and catabolism between MetS-KOA and nMetS-KOA patients. The results showed that MetS-KOA-FLS expressed higher levels of chemokines (CXCL8, CCL2 and CCL3) (Fig. 1b), intercellular cell adhesion molecule 1 (ICAM1) and vascular cell adhesion molecule 1(VCAM1) (Fig. 1c), inflammatory cytokines (TNFα and IL-6) (Fig. 1d), angiogenesis-associated vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) (Fig. 1e) and related to degradation and damage of cartilage matrix metalloproteinase 13 (MMP13) and a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) (Fig. 1f) with the analysis of quantitative real-time PCR (qRT-PCR) and ELISA. In addition, we confirmed that MetS-KOA-FLS has stronger adhesion and invasion abilities through cell adhesion and invasion assessments (Fig. 1g and h).

MetS-KOA-FLS show over-active metabolism of lipid

Recent researches have revealed that cellular metabolism disorders may involved in dysfunction of cells. Here we wonder whether MetS-KOA-FLS have abnormal glucose and lipid metabolism, which results in their excessive pathological phenotypes. The results showed that compared with nMetS-KOA-FLS, MetS-KOA-FLS displayed significantly up-regulated mRNA expressions of the key enzymes of glycolysis such as hexokinase 2 (HK2) and lactate dehydrogenase A (LDHA) (Fig. 2a). Elevated levels of LDHA but not HK2 were further confirmed by the the western blot analysis (Fig. 2b). Next, we also found that the mRNA and protein levels of carnitine palmitoyltransferase 1 A (CPT1A), the rate-limiting enzyme of FAO, were significantly up-regulated in MetS-KOA-FLS (Fig. 2c and d). These results indicate over-active lipid metabolism in MetS-KOA-FLS.

Fig. 2
figure 2

Lipid metabolism is more active in MetS-KOA-FLS. a mRNA levels of glycolysis genes in MetS-KOA-FLS relative to those in nMetS-KOA-FLS. n = 5. b Detection of protein levels of HK2 and LDHA in nMetS-KOA-FLS and MetS-KOA-FLS by WB. n = 3. c mRNA levels of CPT1A in MetS-KOA-FLS relative to that in nMetS-KOA-FLS. n = 5. d Detection of CPT1A protein level in nMetS-KOA-FLS and MetS-KOA-FLS by WB. n = 3. Data are expressed as means ± s.e.m. Statistical significance is indicated as *P < 0.05 and **P < 0.01, as assessed by two-sided Student’s t-test

Full size image

The microenvironment of MetS-KOA promotes inflammation and FAO of FLS

MetS is a systemic risk factor for KOA, and the synovium is the most vascularized tissue in the knee joint. Therefore, we speculated that long-term chronic microenvironment stimulation may lead to abnormal glucolipid metabolism and the phenotype of MetS-KOA-FLS. To test this hypothesis, we stimulated nMetS-KOA-FLS with serum from MetS-KOA. Our data showed that there were higher mRNA expressions of inflammation-related factors and several key catabolic enzymes including CCL3, ICAM1, TNFα, MMP13 and ADAMTS4 in nMetS-KOA-FLS stimulated with MetS-serum (Fig. 3a). We also observed that both mRNA and protein levels of CPT1A were significantly increased in nMetS-KOA-FLS when stimulated with MetS-serum (Fig. 3b and c). Although MetS-serum-treated nMetS-KOA-FLS showed elevated levels of HK2 and reduced levels of LDHA (Fig. 3d), no significant changes were observed in the proteins levels of HK2 and LDHA (Fig. 3e). Taken together, our data suggest that the microenvironment of MetS-KOA results in altered inflammatory phenotypes and metabolic reprogramming of FLS.

Fig. 3
figure 3

MetS-serum promotes inflammation, catabolism, and FAO in nMetS-KOA-FLS.. MetS-KOA serum (5%) was used to stimulate nMetS-KOA-FLS for 24 h (5% FBS was used as control). (Ctrl: 5% FBS, Serum: 5% serum of MetS-KOA, n = 5.) a, mRNA levels of CCL3, ICAM1, TNFα, MMP13 and ADAMTS4 relative to control. b, CPT1A transcription levels in nMetS-KOA-FLS after treatment with 5% serum from MetS-KOA. c, Protein level of CPT1A in nMetS-KOA-FLS after treatment with 5% serum from MetS-KOA. d, mRNA levels of HK2 and LDHA relative to control. e, Protein levels of HK2 and LDHA in nMetS-KOA-FLS after treatment with 5% serum from MetS-KOA. Data are expressed as means ± s.e.m. Statistical significance indicated as *P < 0.05, **P < 0.01, and ***P < 0.001, as assessed by matched samples t- test

Full size image

The expression of CPT1A and resistin is positively correlated with fasting blood-glucose, triglycerides and the number of MetS components in MetS-KOA patients

Abovementioned data showed a increase in the expression of CPT1A in MetS-KOA-FLS, which may be related to the long-term stimulation of the microenvironment of the MetS. Then we analyzed the correlation between the expression of CPT1A and the age of patients and the relevant components of MetS. The results showed that the expression of CPT1A was positively correlated with the number of MetS components, fasting blood glucose (FBG) and triglyceride (TG) levels, but not with age, BMI, waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure (DBP) and high-density lipoprotein cholesterol (HDL-c) levels (Fig. 4a and d).

Fig. 4
figure 4

Correlation analysis between the expression of CPT1A and resistin and MetS components. a Correlation analysis between the mRNA level of CPT1A and age (MetS-KOA: n = 10, nMetS-KOA: n = 10). b Correlation analysis between the mRNA level of CPT1A and BMI (MetS-KOA: n = 10, nMetS-KOA: n = 10). c Correlation analysis between the mRNA level of CPT1A and the number of MetS components (MetS-KOA: n = 10, nMetS-KOA: n = 10). d Correlation analysis between the mRNA level of CPT1A and WC, SBP, DBP, FBG, TG, and HDL-c (MetS-KOA: n = 10, nMetS-KOA: n = 10). e Correlation analysis between the serum resistin and the number of MetS components, FBG, and TG (MetS-KOA: n = 37, nMetS-KOA: n = 43). Statistical significance indicated as P < 0.05, as assessed by pearson correlation analysis

Full size image

Our previous studies have demonstrated that the protein levels of serum resistin in MetS-OA positively correlates with the degree of metabolic disorders [9]. Similarly, we analyzed the correlation between the level of serum resistin and the number of MetS components, FBG, and TG (Fig. 4e). The results showed that resistin was also positively correlated with these clinical indicators. Therefore, we wonder whether the regulation of FLS inflammation and catabolism by the internal environment of MetS patients is mediated by resistin.

Resistin promotes inflammation, catabolism, and FAO in MetS-KOA-FLS

We stimulated MetS-KOA-FLS with recombinant human resistin and observed its effect in inducing inflammation and catabolism in FLS. We observed that resistin had no effect on the proliferation and apoptosis of MetS-KOA-FLS at a concentration of 500 ng/ml (Fig. S1a, b). Meanwhile, the expression of TNFα peaked under 200 ng/ml resistin treatment (Fig. S1c). Therefore, we selected 200 ng/ml resistin for follow-up experiments.

Our results showed that resistin up-regulated the mRNA levels of CCL3, ICAM1, TNFα, MMP13, and ADAMTS4 (Fig. 5a), consistent with the supernatant protein level of CCL3, MMP13, and ADAMTS4 (Fig. 5b). The results of cell adhesion assays and invasion assays show that resistin can promote the adhesion and invasion ability of MetS-KOA-FLS (Fig. 5c and d). These results indirectly confirm that more active inflammation and catabolism of MetS-KOA-FLS mediated by resistin is consistent with those mediated by MetS serum.

Fig. 5
figure 5

Resistin promotes inflammation and catabolism in MetS-KOA-FLS. MetS-KOA-FLS were stimulated with or without 200 ng/ml resistin for 24 h. (Ctrl: 0 ng/ml resistin, Resistin: 200 ng/ml resistin, n = 5.) a, Relative mRNA levels of CCL3, ICAM1, TNFα, MMP13, and ADAMTS4 in MetS-KOA-FLS treated with or without resistin were detected by qRT-PCR. b, MetS-KOA-FLS were treated with resistin for 24 h, and then the protein levels of CCL3, MMP13, and ADAMTS4 in the culture supernatant were measured by ELISA c, MetS-KOA-FLS stimulated with or without 200 ng/ml resistin for 24 h were then co-cultured (1:3) with THP-1 cells for 6 h. The number of adherent THP-1 cells was shown on the right. d, MetS-KOA-FLS stimulated with and without 200 ng/ml resistin for 72 h were subjected to invasion assay. e, mRNA and protein level of CPT1A in MetS-KOA-FLS treated with or without resistin were detected by qRT-PCR and western blot. f, Relative mRNA levels of HK and LDHA in MetS-KOA-FLS treated with or without resistin were detected by qRT-PCR. g, Protein levels of HK2 and LDHA in MetS-KOA-FLS treated with or without resistin were detected by western blot. Data are expressed as means ± s.e.m. Statistical significance indicated as *P < 0.05, and**P < 0.01, and ***P < 0.001, as assessed by matched samples t- test

Full size image

Next, we detected the expression of key enzymes in glucose and fatty acid metabolism pathways in resistin-stimulated MetS-KOA-FLS. The results showed that both the mRNA and protein levels of CPT1A were significantly up-regulated in resistin-stimulated MetS-KOA-FLS (Fig. 5e). However, resistin-stimulated MetS-KOA-FLS displayed up-regulated HK2 and down-regulated LDHA (Fig. 5f). More importantly, the protein expression of HK2 and LDHA did not change significantly after resistin stimulation (Fig. 5g).

Resistin promotes inflammation and catabolism by upregulating the FAO of MetS-KOA-FLS

To clarify whether increased FAO mediated by resistin directly promote inflammation and catabolism of MetS-KOA-FLS, we pretreated MetS-KOA-FLS with 100 µM Etomoxir (Eto), an irreversible inhibitor of CPT1, and then incubated with resistin for 24 h. Our results showed that both the mRNA and protein levels of inflammation-related factors (CCL3, ICAM1, TNFα) and catabolic enzymes (MMP13, ADAMTS4) as well as the ability of adhesion and invasion were all significantly enhanced in resistin-stimulated MetS-KOA-FLS. However, in the presence of Eto, these abovementioned features in MetS-KOA-FLS induced by resistin were inhibited (Fig. 6). These results suggest that the promotion of inflammation and catabolism of MetS-KOA-FLS induced by resistin may mainly be relied on increased FAO.

Fig. 6
figure 6

Resistin promotes inflammation and catabolism by upregulating FAO in MetS-KOA-FLS. MetS-KOA-FLS were pre-incubated with 100 µM Eto for 2 h and then incubated with 200 ng/ml resistin for 24 h to detect changes in inflammation and catabolism. Eto, Etomoxir. n = 5. a mRNA levels of CCL3ICAM1 and TNFα, and protein levels of CCL3 in the supernatant. b mRNA levels of MMP13 and ADAMTS4, and protein levels of MMP13 and ADAMTS4 in the supernatant. c, Count of THP-1 co-cultured (3:1) with MetS-KOA-FLS for 6 h. d Quantitfication of MetS-KOA-FLS invasion. Data are expressed as means ± s.e.m. Statistical significance indicated as *P < 0.05, **P < 0.01 and ***P < 0.001; matched samples t- test was used

Full size image

In addition, 10 mM 2-deoxy-d-glucose (2-DG) was also applied to inhibit the glucose metabolism of MetS-KOA-FLS. Interestingly, resistin promoted inflammation and catabolism of MetS-KOA-FLS, and the combined application of the two led to further enhancement of the both functions (Fig. S2).

Resistin promotes FAO of MetS-KOA-FLS through the CAP1/PKA/CREB pathway

In order to further investigate the specific mechanisms by which resistin promotes the FAO of MetS-KOA-FLS, we first detected the expression of resistin receptors on MetS-KOA-FLS and nMetS-KOA-FLS. Toll like receptor 4 (TLR4) and adenylyl cyclase-associated protein 1 (CAP1) are the major receptors for resistin in humans [17]. We found that the mRNA expression of TLR4 was significantly upregulated in MetS-KOA-FLS than nMetS-KOA-FLS, but no difference in protein level was observed (Fig. 7a). However, both mRNA and protein levels of CAP1 were up-regulated in MetS-KOA-FLS compared to nMetS-KOA-FLS (Fig. 7b), which was further confirmed by higher expressions of CAP1 in synovium with the analysis of immunohistochemistry (Fig. 7c). When we applied small interfering RNA (siRNA) to knock down the expression of CAP1 (Fig. 7e), we found that up-regulated expression of CPT1A in MetS-KOA-FLS induced by resistin was significantly inhibited (Fig. 7f and g). However, the treatment of TAK-242 (an inhibitor of TLR4) could not inhibit the up-regulation of CPT1A (Fig. 7d). This suggests that resistin-CAP1 but not resistin-TLR4 may be involved in MetS-KOA-FLS.

Fig. 7
figure 7

Resistin promotes the expression of CPT1A through CAP1/PKA/CREB. a In vitro protein and mRNA levels of TLR4 in nMetS-KOA-FLS and MetS-KOA-FLS. b In vitro protein and mRNA levels of CAP1 in nMetS-KOA-FLS and MetS-KOA-FLS. c Immunohistochemistry of CAP1 in synovium of nMetS-KOA and MetS-KOA. d, mRNA and protein levels of CPT1A in MetS-KOA-FLS pretreated with 10 nM TAK-242 for 1 h and then incubated with 200 ng/ml resistin for 24 h. e mRNA and protein levels of CAP1 in MetS-KOA-FLS 48 h after transfection with CAP1-siRNA. f Protein levels of CAP1 and CPT1A in MetS-KOA-FLS transfected with CAP1-siRNA for 48 h and incubated with 200 ng/ml resistin for 24 h. g mRNA levels of CPT1A in MetS-KOA-FLS transfected with CAP1-siRNA for 48 h and incubated with 200 ng/ml resistin for 24 h. h Protein levels of CREB and pCREBser133 in MetS-KOA-FLS transfected with CAP1-siRNA for 48 h and incubated with 200 ng/ml resistin for 24 h. i mRNA level of CPT1A in MetS-KOA-FLS pretreated with 2.5 µM KG-501 or 2.5 µM H-89 for 1 h and then incubated with 200 ng/ml resistin for 24 h. j Protein levels of CREB, pCREBser133, and CPT1A in MetS-KOA-FLS pretreated with 2.5 µM KG-501 or 2.5 µM H-89 for 1 h and then incubated with 200 ng/ml resistin for 24 h. k mRNA levels of CCL3, ICAM1 and TNFα in MetS-KOA-FLS pretreated with 2.5 µM KG-501 or 2.5 µM H-89 for 1 h and then incubated with 200 ng/ml resistin for 24 h. l mRNA levels of MMP13 and ADAMTS4 in MetS-KOA-FLS pretreated with 2.5 µM KG-501 or 2.5 µM H-89 for 1 h and then incubated with 200 ng/ml resistin for 24 h. Data are expressed as means ± s.e.m. n = 5 biologically independent samples of MetS-KOA-FLS. Statistical significance indicated as *P < 0.05, **P < 0.01, and ***P < 0.001, as assessed by matched samples t- test

Full size image

Here we found that resistin promoted expression of pCREBser133 in MetS-KOA-FLS, which was inhibited when CAP1 was knocked down by CAP1-siRNA (Fig. 7h). Furthermore, KG-501, a functional inhibitor of pCREBser133, could abrogate resistin-induced CPT1A expression without affecting the phosphorylation of CREB-Ser (133) (Fig. 7i and j). In addition, the treatment of H-89 (a PKA inhibitor) inhibited the expression of CPT1A and the phosphorylation of CREB resistin-treated MetS-KOA-FLS (Fig. 7i and j). Finally, the impact of H-89 or KG-501 on resistin-induced inflammation and catabolism was examined. The findings revealed that both H-89 and KG-501 effectively suppressed the mRNA levels of resistin-induced inflammation-related factors (CCL3, ICAM1, TNFα) and catabolic enzymes (MMP13, ADAMTS4) (Fig. 7k and l).

In summary, our results suggest that resistin may binds to CAP1 in MetS-KOA-FLS to activate PKA, which in turn phosphorylates and activates CREB. pCREBser133 upregulates CPT1A to increase cellular FAO, which in turn promotes abberant inflammatory characteristics in MetS-KOA-FLS (Fig. 8).

Fig. 8
figure 8

Resistin regulates inflammation and catabolism by promoting FAO of MetS-KOA-FLS via CAP1/PKA/CREB. Resistin binds to CAP1 to activate PKA, which in turn phosphorylates CREB-Ser (133). Phosphorylation of CREB-Ser (133) increases its transcriptional activity and promotes the transcription of CPT1A. Increased expression of CPT1A can promote the transport of free fatty acids to mitochondria, which may increase cellular FAO. This upregulation of FAO in MetS-KOA-FLS further promotes inflammation and catabolism

Full size image

Discussion

The link between MetS and OA has been definitively demonstrated in numerous studies [18]. However, the intrinsic mechanism of this association and the key factors involved remain unknown. In this study, we found that in microenvironment of MetS, KOA-FLS had more active inflammation, catabolism and FAO. More importantly, we showed that resistin binding to its receptors CAP1 enhanced FAO via the activation of PKA/CREB signal pathway, which leads to the promotion of inflammation and catabolism of MetS-KOA-FLS.

The synovium is a highly vascularized tissue with a rich blood supply, and therefore more susceptible to systemic factors than cartilage tissues that lack vascular nourishment [19]. Previous in vivo experiments have demonstrated that a high-carbohydrate and high-fat diet aggravated the development of synovitis, and synovial inflammatory changes were likely to appear before cartilage degeneration [20, 21, 22]. As MetS is a systemic factor of OA, researchers should be particularly focused on its impact on OA synovitis, especially key target cells FLS. Our results revealed that MetS-KOA-FLS displayed more elevated inflammatory and catabolic phenotypes. This further confirms that MetS may be one of key factors which promote the development of synovitis.

In MetS microenviroment, free fatty acids [23, 24, 25, 26], hyperglycemia [27], hyperinsulinemia [28], advanced glycation end products [29] and adipokines [30] may be important facors which can affect the inflammation and catabolism of KOA-FLS. In our study, we illustrated that MetS-KOA-FLS expressed higher levels of CPT1A, key enzymes of FAO, which were further increased when stimulated with MetS serum. Our data indicate that FAO may be crucial for inducing the inflammation and catabolism in MetS-KOA-FLS. We still found that the mRNA expression of CPT1A was positively correlated with the number of MetS components, TG and FBG, which indicates that the more severe the metabolic disorder was, the higher the expression of CPT1A was. This may be due to the fact that TG in serum increases the substrate level of cell FAO, thus promoting cell FAO. And the up-regulation of cell FAO makes cell energy metabolism incline towards lipid metabolism, and reduces the utilization of glucose, which leads to the accumulation of blood glucose in serum.

Growing evidence suggests that metabolic factors, particularly adipokines, play prominent roles in the pathophysiology of OA [31]. Resistin, first identified in a mouse model of diabetes, was described as a novel adipokine [32]. As a molecular link between metabolic signaling and inflammation, resistin is thought to play an important role in metabolic stress-induced inflammatory states associated with excess caloric intake [33]. In our previous study, resistin was found to be increased in the serum of OA patients, positively correlated with the severity of MetS [9, 34]. The higher level of serum resistin was associated with knee synovitis in KOA [35, 36]. Our results in this study showed that the level of resistin in serum was also positively correlated with the number of MetS components, TG, and FBG. This indicates that the level of resistin is related to the disorder of glucose and lipid metabolism. The imbalance of glucose and lipid metabolism of MetS-KOA-FLS may be related to the high level of resistin in serum.

Our present study showed that resistin could promote the expression of chemokines, adhesion factors, inflammatory factors, and catabolic enzymes of MetS-KOA-FLS which further confirms the effect of resistin on FLS in the study by Chen and Cheleschi et al. [37, 38] More importantly, we showed that FAO inhibition suppressed the up-regulation of inflammatory phenotypes in resistin-stimulated MetS-KOA-FLS. Previous relevant studies have shown that the efficiency of fatty acid uptake and FAO were decreased in 3T3-L1, L6, and C2C12 cells stimulated with resistin [12, 13, 14]. The differential effects mediated by resistin may be due to tissue specificity and species heterogeneity. Our data suggest that resistin may be the main active substance in MetS-serum responsible for increased FAO which results in abberrant proinflammatory phenotypes of FLS.

TLR4 and CAP1 have been proposed as possible functional resistin receptors in human monocytes [39]. Direct binding of resistin and CAP1 was demonstrated by co-immunoprecipitation in both Lee et al. and our previous study [40, 34]. In this study, we displayed that CAP1 was highly expressed in MetS-KOA-FLS, and resistin-induced upregulation of FAO in MetS-KOA-FLS was impaired when CAP1 was knocked down. These results indicate that CAP1, but not TLR4, may act as a functional receptor for resistin to modulate phenotypic changes in MetS-KOA-FLS. The cAMP/PKA pathway is considered to be the main downstream signaling pathway of CAP1 [40]. Increased intracellular levels of cAMP lead to the activation of the cAMP-response element-binding protein (CREB) [41]. CREB can be phosphorylated at serine residue 133 (Ser-133) by activated PKA, which allows the recruitment of CREB-binding protein (CBP) or its analog p300, enhancing transcriptional activity [42]. And CREB has been reported to be involved in the activation of FAO [43]. Our results showed that CAP1-siRNA, H-89, and KG-501 all inhibited resistin-induced up-regulation of CPT1A expression, and CAP1-siRNA and H-89 also inhibited the phosphorylation of CREB. These results suggest that the binding of resistin to CAP1 activates PKA and promotes the phosphorylation of CREB, which in turn upregulates the expression of CPT1A and promotes the FAO of MetS-KOA-FLS.

Conclusions

In summary, in MetS microenvironment, increased FAO contributes to synovial inflammation and catabolism of MetS-KOA-FLS, which is predominantly mediated by resistin binding to its functional receptors CAP1 via the activation of PKA/CREB signal pathway. The results of this study provide feasibility for finding the common metabolic mechanism of MetS and KOA, and provide new ideas for individualized treatment of MetS-KOA patients.

Data availability

No datasets were generated or analysed during the current study.

Abbreviations

OA:

Osteoarthritis

MetS:

Metabolic syndrome

KOA:

Knee osteoarthritis

FLS:

Fibroblast-like synoviocytes

FAO:

Fatty acid oxidation

HE:

Hematoxylin and eosin

MMP:

matrix metalloproteinase

ADAMTS:

A disintegrin and metalloproteinase with thrombospondin motifs

IL:

Interleukin

CCL:

C-C motif chemokine ligand

ICAM:

intercellular cell adhesion molecule

VCAM:

Vascular cell adhesion molecule

VEGF:

Vascular endothelial growth factor

FGF:

Fibroblast growth factor

HK:

Hexokinase

LDH:

Lactate dehydrogenase

CPT:

Carnitine palmitoyltransferase

FBG:

Fasting blood glucose

TG:

Triglyceride

WC:

Waist circumference

SBP:

Systolic blood pressure

DBP:

Diastolic blood pressure

HDL-c:

High-density lipoprotein cholesterol

Eto:

Etomoxir

2-DG:

2-deoxy-D-glucose

TLR:

Toll like receptor

CAP:

Cyclase-associated protein

cAMP:

cyclic adenosine monophosphate

CREB:

cAMP-response element-binding protein

CBP:

CREB-binding protein

References

  1. Loeser RF, Goldring SR, Scanzello CR, Goldring MB. Osteoarthritis: a disease of the joint as an organ. Arthritis Rheum. 2012;64:1697–707. https://doiorg.publicaciones.saludcastillayleon.es/10.1002/art.34453.

    Article  PubMed  PubMed Central  Google Scholar 

  2. Suri P, Morgenroth DC, Hunter DJ. Epidemiology of osteoarthritis and associated comorbidities. PM R. 2012;4:S10–9. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.pmrj.2012.01.007.

    Article  PubMed  Google Scholar 

  3. Walrabenstein W, Wagenaar CA, van de Put M, van der Leeden M, Gerritsen M, Twisk JWR, et al. A multidisciplinary lifestyle program for metabolic syndrome-associated osteoarthritis: the plants for joints randomized controlled trial. Osteoarthritis Cartilage. 2023. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.joca.2023.05.014.

    Article  PubMed  Google Scholar 

  4. Eckel RH, Grundy SM, Zimmet PZ. The metabolic syndrome. Lancet. 2005;365:1415–28.

    Article  CAS  PubMed  Google Scholar 

  5. Liu SY, Zhu WT, Chen BW, Chen YH, Ni GX. Bidirectional association between metabolic syndrome and osteoarthritis: a meta-analysis of observational studies. Diabetol Metab Syndr. 2020;12:38. https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s13098-020-00547-x.

    Article  PubMed  PubMed Central  Google Scholar 

  6. Berenbaum F. Osteoarthritis as an inflammatory disease (osteoarthritis is not osteoarthrosis!). Osteoarthritis Cartilage. 2013;21:16–21. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.joca.2012.11.012.

    Article  CAS  PubMed  Google Scholar 

  7. Sellam J, Berenbaum F. The role of synovitis in pathophysiology and clinical symptoms of osteoarthritis. Nat Rev Rheumatol. 2010;6:625–35. https://doiorg.publicaciones.saludcastillayleon.es/10.1038/nrrheum.2010.159.

    Article  CAS  PubMed  Google Scholar 

  8. Pap T, Dankbar B, Wehmeyer C, Korb-Pap A, Sherwood J. Synovial fibroblasts and articular tissue remodelling: role and mechanisms. Semin Cell Dev Biol. 2020;101:140–5. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.semcdb.2019.12.006.

    Article  CAS  PubMed  Google Scholar 

  9. Ding L, Gao YH, Li YR, Huang YF, Wang XY, Qi X. Metabolic score for insulin resistance is correlated to adipokine disorder and inflammatory activity in female knee osteoarthritis patients in a Chinese population. Diabetes Metab Syndr Obes. 2020;13:2109–18. https://doiorg.publicaciones.saludcastillayleon.es/10.2147/DMSO.S249025.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  10. Bostrom EA, Svensson M, Andersson S, Jonsson IM, Ekwall AK, Eisler T, et al. Resistin and insulin/insulin-like growth factor signaling in rheumatoid arthritis. Arthritis Rheum. 2011;63:2894–904. https://doiorg.publicaciones.saludcastillayleon.es/10.1002/art.30527.

    Article  CAS  PubMed  Google Scholar 

  11. Di Simone N, Di Nicuolo F, Marzioni D, Castellucci M, Sanguinetti M, D’Lppolito S, et al. Resistin modulates glucose uptake and glucose transporter-1 (GLUT-1) expression in trophoblast cells. J Cell Mol Med. 2009;13:388–97. https://doiorg.publicaciones.saludcastillayleon.es/10.1111/j.1582-4934.2008.00337.x.

    Article  CAS  PubMed  Google Scholar 

  12. He F, Jin JQ, Qin QQ, Zheng YQ, Li TT, Zhang Y, et al. Resistin regulates fatty acid Beta oxidation by suppressing expression of peroxisome proliferator activator receptor Gamma-Coactivator 1alpha (PGC-1alpha). Cell Physiol Biochem. 2018;46:2165–72. https://doiorg.publicaciones.saludcastillayleon.es/10.1159/000489546.

    Article  CAS  PubMed  Google Scholar 

  13. Palanivel R, Sweeney G. Regulation of fatty acid uptake and metabolism in L6 skeletal muscle cells by resistin. FEBS Lett. 2005;579:5049–54. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.febslet.2005.08.011.

    Article  CAS  PubMed  Google Scholar 

  14. Ikeda Y, Tsuchiya H, Hama S, Kajimoto K, Kogure K. Resistin affects lipid metabolism during adipocyte maturation of 3T3-L1 cells. FEBS J. 2013;280:5884–95. https://doiorg.publicaciones.saludcastillayleon.es/10.1111/febs.12514.

    Article  CAS  PubMed  Google Scholar 

  15. Hall CJ, Sanderson LE, Lawrence LM, Pool B, van der Kroef M, Ashimbayeva E, et al. Blocking fatty acid-fueled mROS production within macrophages alleviates acute gouty inflammation. J Clin Invest. 2018;128:1752–71. https://doiorg.publicaciones.saludcastillayleon.es/10.1172/JCI94584.

    Article  PubMed  PubMed Central  Google Scholar 

  16. Krenn V, Morawietz L, Burmester GR, Kinne RW, Mueller-Ladner U, Muller B, Haupl T. Synovitis score: discrimination between chronic low-grade and high-grade synovitis. Histopathology. 2006;49(4):358–64. https://doiorg.publicaciones.saludcastillayleon.es/10.1111/j.1365-2559.2006.02508.x.

    Article  CAS  PubMed  Google Scholar 

  17. ZCW, GYH, SWX, LB, DL, DN, et al. An update on the emerging role of resistin on the pathogenesis of osteoarthritis. Mediators Inflamm. 2019;2019:1532164. https://doiorg.publicaciones.saludcastillayleon.es/10.1155/2019/1532164.

  18. Reyes C, Leyland KM, Peat G, Cooper C, Arden NK, Prieto-Alhambra D. Association between overweight and obesity and risk of clinically diagnosed knee, hip, and hand osteoarthritis: A Population-Based cohort study. Arthritis Rheumatol. 2016;68:1869–75. https://doiorg.publicaciones.saludcastillayleon.es/10.1002/art.39707.

    Article  PubMed  PubMed Central  Google Scholar 

  19. Hugle T, Geurts J. What drives osteoarthritis?-synovial versus subchondral bone pathology. Rheumatology (Oxford). 2017;56:1461–71. https://doiorg.publicaciones.saludcastillayleon.es/10.1093/rheumatology/kew389.

    Article  CAS  PubMed  Google Scholar 

  20. Larranaga-Vera A, Lamuedra A, Perez-Baos S, Prieto-Potin I, Pena L, Herrero-Beaumont G, et al. Increased synovial lipodystrophy induced by high fat diet aggravates synovitis in experimental osteoarthritis. Arthritis Res Ther. 2017;19:264. https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s13075-017-1473-z.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  21. Sun AR, Panchal SK, Friis T, Sekar S, Crawford R, Brown L, et al. Obesity-associated metabolic syndrome spontaneously induces infiltration of pro-inflammatory macrophage in synovium and promotes osteoarthritis. PLoS ONE. 2017;12:e0183693. https://doiorg.publicaciones.saludcastillayleon.es/10.1371/journal.pone.0183693.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  22. de Visser HM, Mastbergen SC, Kozijn AE, Coeleveld K, Pouran B, van Rijen MH, et al. Metabolic dysregulation accelerates injury-induced joint degeneration, driven by local inflammation; an in vivo rat study. J Orthop Res. 2018;36:881–90. https://doiorg.publicaciones.saludcastillayleon.es/10.1002/jor.23712.

    Article  CAS  PubMed  Google Scholar 

  23. Baker KR, Matthan NR, Lichtenstein AH, Niu J, Guermazi A, Roemer F, et al. Association of plasma n-6 and n-3 polyunsaturated fatty acids with synovitis in the knee: the MOST study. Osteoarthritis Cartilage. 2012;20:382–7. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.joca.2012.01.021.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  24. Wu CL, Kimmerling KA, Little D, Guilak F. Serum and synovial fluid lipidomic profiles predict obesity-associated osteoarthritis, synovitis, and wound repair. Sci Rep. 2017;7:44315. https://doiorg.publicaciones.saludcastillayleon.es/10.1038/srep44315.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  25. Alvarez-Garcia O, Rogers NH, Smith RG, Lotz MK. Palmitate has proapoptotic and Proinflammatory effects on articular cartilage and synergizes with interleukin-1. Arthritis Rheumatol. 2014;66:1779–88. https://doiorg.publicaciones.saludcastillayleon.es/10.1002/art.38399.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  26. de Seny D, Cobraiville G, Charlier E, Neuville S, Lutteri L, Le Goff C, et al. Apolipoprotein-A1 as a damage-associated molecular patterns protein in osteoarthritis: ex vivo and in vitro pro-inflammatory properties. PLoS ONE. 2015;10:e0122904. https://doiorg.publicaciones.saludcastillayleon.es/10.1371/journal.pone.0122904.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  27. Gui T, Lin YK, Huan SW, Li YH, Wang BH, Yang J, et al. Elevated expression of ICAM-1 in synovium is associated with early inflammatory response for cartilage degeneration in type 2 diabetes mellitus. J Cell Biochem. 2019;120:13177–86. https://doiorg.publicaciones.saludcastillayleon.es/10.1002/jcb.28592.

    Article  CAS  PubMed  Google Scholar 

  28. Qiao L, Li Y, Sun S. Insulin exacerbates inflammation in Fibroblast-Like synoviocytes. Inflammation. 2020;43:916–36. https://doiorg.publicaciones.saludcastillayleon.es/10.1007/s10753-020-01178-0.

    Article  CAS  PubMed  Google Scholar 

  29. Li Q, Wen Y, Wang L, Chen B, Chen J, Wang H, et al. Hyperglycemia-induced accumulation of advanced glycosylation end products in fibroblast-like synoviocytes promotes knee osteoarthritis. Exp Mol Med. 2021;53:1735–47. https://doiorg.publicaciones.saludcastillayleon.es/10.1038/s12276-021-00697-6.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  30. Chen WC, Lu YC, Kuo SJ, Lin CY, Tsai CH, Liu SC, et al. Resistin enhances IL-1beta and TNF-alpha expression in human osteoarthritis synovial fibroblasts by inhibiting miR-149 expression via the MEK and ERK pathways. FASEB J. 2020;34:13671–84. https://doiorg.publicaciones.saludcastillayleon.es/10.1096/fj.202001071R.

    Article  CAS  PubMed  Google Scholar 

  31. Francisco V, Ruiz-Fernandez C, Pino J, Mera A, Gonzalez-Gay MA, Gomez R, et al. Adipokines: linking metabolic syndrome, the immune system, and arthritic diseases. Biochem Pharmacol. 2019;165:196–206. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.bcp.2019.03.030.

    Article  CAS  PubMed  Google Scholar 

  32. Steppan CM, Bailey ST, Bhat S, Brown EJ, Banerjee RR, Wright CM, et al. The hormone resistin links obesity to diabetes. Nature. 2001;409:307–12. https://doiorg.publicaciones.saludcastillayleon.es/10.1038/35053000.

    Article  CAS  PubMed  Google Scholar 

  33. Abate N, Sallam HS, Rizzo M, Nikolic D, Obradovic M, Bjelogrlic P, et al. Resistin: an inflammatory cytokine. Role in cardiovascular diseases, diabetes and the metabolic syndrome. Curr Pharm Des. 2014;20:4961–9. https://doiorg.publicaciones.saludcastillayleon.es/10.2174/1381612819666131206103102.

    Article  CAS  PubMed  Google Scholar 

  34. Zhao CW, Song WX, Liu B, Gao YH, Ding L, Huang YF, et al. Resistin induces chemokine and matrix metalloproteinase production via CAP1 receptor and activation of p38-MAPK and NF-kappaB signalling pathways in human chondrocytes. Clin Exp Rheumatol. 2022;40:501–13. https://doiorg.publicaciones.saludcastillayleon.es/10.55563/clinexprheumatol/avcj31.

    Article  PubMed  Google Scholar 

  35. Han W, Aitken D, Zheng S, Wang B, Wluka AE, Zhu Z, et al. Higher serum levels of resistin are associated with knee synovitis and structural abnormalities in patients with symptomatic knee osteoarthritis. J Am Med Dir Assoc. 2019;20:1242–6. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.jamda.2019.07.001.

    Article  PubMed  Google Scholar 

  36. de Boer TN, van Spil WE, Huisman AM, Polak AA, Bijlsma JW, Lafeber FP, et al. Serum adipokines in osteoarthritis; comparison with controls and relationship with local parameters of synovial inflammation and cartilage damage. Osteoarthritis Cartilage. 2012;20:846–53. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.joca.2012.05.002.

    Article  PubMed  Google Scholar 

  37. Chen WC, Wang SW, Lin CY, Tsai CH, Fong YC, Lin TY, et al. Resistin enhances monocyte chemoattractant Protein-1 production in human synovial fibroblasts and facilitates monocyte migration. Cell Physiol Biochem. 2019;52:408–20. https://doiorg.publicaciones.saludcastillayleon.es/10.33594/000000029.

    Article  CAS  PubMed  Google Scholar 

  38. Cheleschi S, Gallo I, Barbarino M, Giannotti S, Mondanelli N, Giordano A, et al. MicroRNA mediate visfatin and resistin induction of oxidative stress in human Osteoarthritic synovial fibroblasts via NF-kappaB pathway. Int J Mol Sci. 2019;20. https://doiorg.publicaciones.saludcastillayleon.es/10.3390/ijms20205200.

  39. Huang X, Yang Z. Resistin’s, obesity and insulin resistance: the continuing disconnect between rodents and humans. J Endocrinol Invest. 2016;39:607–15. https://doiorg.publicaciones.saludcastillayleon.es/10.1007/s40618-015-0408-2.

    Article  CAS  PubMed  Google Scholar 

  40. Lee S, Lee HC, Kwon YW, Lee SE, Cho Y, Kim J, et al. Adenylyl cyclase-associated protein 1 is a receptor for human resistin and mediates inflammatory actions of human monocytes. Cell Metab. 2014;19:484–97. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.cmet.2014.01.013.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  41. Grossmann C, Ruhs S, Seiferth A, Gekle M. Interaction between mineralocorticoid receptor and cAMP/CREB signaling. Steroids. 2010;75:539–43. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.steroids.2009.10.006.

    Article  CAS  PubMed  Google Scholar 

  42. Johannessen M, Delghandi MP, Moens U. What turns CREB on? Cell Signal. 2004;16:1211–27. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.cellsig.2004.05.001.

    Article  CAS  PubMed  Google Scholar 

  43. Wang B, Zhu L, Sui S, Sun C, Jiang H, Ren D. Cilostazol induces mitochondrial fatty acid beta-oxidation in C2C12 myotubes. Biochem Biophys Res Commun. 2014;447:441–5. https://doiorg.publicaciones.saludcastillayleon.es/10.1016/j.bbrc.2014.04.028.

    Article  CAS  PubMed  Google Scholar 

Download references

Acknowledgements

We extend sincere gratitude to the staff of the Department of Orthopaedic Surgery and Dalian key laboratory of human microorganism homeostasis and immunological mechanism research of diseases for their assistance during this study. We thank the Department of Biobank, Division of Clinical Research，The first hospital of Jilin University for the providing of human specimens. We would like to thank BioRender for providing the cons. Figure 8 was created with BioRender.com. We also would like to thank Editage (www.editage.cn) for English language editing.

Funding

This work was supported by the National Natural Science Foundation of China (grant numbers 82071834, 82101896, 82271839); the Natural Science Funding of Jilin province (Grant number: 20200201548JC; 20210101324JC) and Medicine & Health Funding of Jilin province (Grant number: 20200404145YY) and International Collabration Funding of Jilin province (Grant number: 20200801045GH); Dalian Medical University Interdisciplinary Research Cooperation Project Team Funding JCHZ2023010; Liaoning Provincial Education Department Basic Research Project(LJ212410161034）.

Author information

Author notes

  1. Lu Dinga and Jin-Yi Ren contributed equally to this work.

Authors and Affiliations

  1. Department of Orthopedic Surgery, The First Hospital of Jilin University, Jilin University, Changchun, 130021, Jilin, China

    Lu Ding, Yi-Fan Huang, Jian-Zeng Zhang, Yi Leng, Jun-Wei Tian & Xin Qi

  2. Department of Immunology, College of Basic Medical Science, Dalian Medical University, Dalian, 116044, Liaoning, China

    Lu Ding, Jin-Yi Ren, Yi-Fan Huang, Zi-Ran Bai, Jing Wei, Min-Li Jin, Guan Wang & Xia Li

Authors
  1. Lu Ding
    View author publications

    You can also search for this author inPubMed Google Scholar

  2. Jin-Yi Ren
    View author publications

    You can also search for this author inPubMed Google Scholar

  3. Yi-Fan Huang
    View author publications

    You can also search for this author inPubMed Google Scholar

  4. Jian-Zeng Zhang
    View author publications

    You can also search for this author inPubMed Google Scholar

  5. Zi-Ran Bai
    View author publications

    You can also search for this author inPubMed Google Scholar

  6. Yi Leng
    View author publications

    You can also search for this author inPubMed Google Scholar

  7. Jun-Wei Tian
    View author publications

    You can also search for this author inPubMed Google Scholar

  8. Jing Wei
    View author publications

    You can also search for this author inPubMed Google Scholar

  9. Min-Li Jin
    View author publications

    You can also search for this author inPubMed Google Scholar

  10. Guan Wang
    View author publications

    You can also search for this author inPubMed Google Scholar

  11. Xia Li
    View author publications

    You can also search for this author inPubMed Google Scholar

  12. Xin Qi
    View author publications

    You can also search for this author inPubMed Google Scholar

Contributions

Lu Ding, Jinyi Ren, Guan Wang, Yifan Huang, Xia Li, and Xin Qi participated in the research design. Lu Ding, Yifan Huang, Yi Leng, and Junwei Tian conducted experiments. Guan Wang, Ziran Bai, Jing Wei, Minli Jin, and Xia Li contributed reagents or analytic tools. Lu Ding, Jinyi Ren, Guan Wang, Yifan Huang, Ziran Bai, Jianzeng Zhang, Xia Li, and Xin Qi performed data analysis and figure generation. Lu Ding, Jinyi Ren, Guan Wang, Xia Li, and Xin Qi were the primary writers of the paper, with contributions from all authors. All authors read and approved the final manuscript.

Corresponding authors

Correspondence to Guan Wang, Xia Li or Xin Qi.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ding, L., Ren, JY., Huang, YF. et al. Resistin upregulates fatty acid oxidation in synoviocytes of metabolic syndrome-associated knee osteoarthritis via CAP1/PKA/CREB to promote inflammation and catabolism. Arthritis Res Ther 27, 99 (2025). https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s13075-025-03527-6

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doiorg.publicaciones.saludcastillayleon.es/10.1186/s13075-025-03527-6

Keywords

Arthritis Research & Therapy

ISSN: 1478-6362

Contact us