Lipogenesis in myoblasts and its regulation of CTRP6 by AdipoR1/Erk/PPARγ signaling pathway

Circulating levels of C1q/TNF-α-related protein 6 (CTRP6) in coronary artery disease and its correlation with inflammatory markers

Introduction

Circulating levels of C1q/TNF-α-related protein 6 (CTRP6) is an adipokine that is involved in regulation of glucose and lipid metabolism, inflammation, and insulin sensitivity. However, the exact role of CTRP6 in metabolic processes remains unclear due to conflicting findings. To address current gap, we aimed to investigate the serum levels of CTRP6 in patients with coronary artery disease (CAD) and its association with inflammatory cytokines.

Method

In this case-control study, the serum levels of CTRP6, interlukin-6 (IL-6), tumor necrosis factor- α (TNF-α), adiponectin, and fasting insulin were measured using enzyme-linked immunosorbent assay (ELISA) kits in a total of 176 participants, consisting of 88 CAD patients and 88 control subjects. Additionally, various anthropometric and biochemical measurements were measured and compared between cases and controls.

Results

The present study found that serum levels of CTRP6 were significantly higher in the CAD group (561.3 ± 15.14) compared to the control group (429.3 ± 12.85, p < 0.001). After adjusting for age, sex, and body mass index (BMI), CTRP6 levels were found to be positively associated with the risk of CAD (p < 0.001). Correlation analysis in CAD subjects revealed a positive correlation between CTRP6 levels and BMI, systolic blood pressure (SBP), malondialdehyde (MDA), TNF-α, and IL-6, as well as a negative correlation with creatinine and total anti-oxidant capacity.

Conclusion

The findings of this study provide novel evidence that elevated serum levels of CTRP6 are significantly associated with an increased risk of developing CAD. Moreover, our results indicate a correlation between CTRP6 and various risk factors for atherosclerosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-024-01415-5.

CTRP6 regulates M1 macrophage polarization via the PPAR-γ/NF-κB pathway and reprogramming glycolysis in recurrent spontaneous abortion

Aberrant polarization and functions of decidual macrophages are closely related to recurrent spontaneous abortion (RSA). C1q/tumor necrosis factor-related protein 6 (CTRP6) is a member of the adiponectin paralog family, and plays indispensable roles in inflammation, glucose uptake and tumor metastasis. However, the regulatory effect of CTRP6 on macrophage polarization and glycolysis in RSA and the underlying mechanisms have not been fully elucidated. In the present study, we first found that CTRP6 expression was positively correlated with the M1 macrophage marker (CD86) in decidual tissues by dual immunofluorescence analysis. In vitro experiments indicated that CTRP6 could facilitate M1 macrophage activation through the PPAR-γ/NF-κB pathway and manipulate the glycolysis of macrophages. Notably, in addition to silencing CTRP6, treatment with a PPAR-γ agonist (GW1929) inhibited M1 macrophage polarization and rescued embryo absorption in vivo. Taken together, these results identify previously unrevealed functions of CTRP6 in macrophage transformation during RSA.

Rapid direct conversion of bovine non-adipogenic fibroblasts into adipocyte-like cells by a small-molecule cocktail

Introduction: The molecular regulation mechanism of fat deposition in bovine and its improvement on beef quality are important research directions in the livestock industry. The research of molecular mechanisms that govern the regulation and differentiation of adipocytes may conduct to understand the mechanism of obesity, lipid disorders, and fat deposition. In the recent decade, small-molecule compounds have been widely used in reprogramming and transdifferentiation fields, which can promote the induction efficiency, replace exogenous genes, or even induce cell fate conversion alone. Furthermore, small-molecule compound induction is expected to be a novel approach to generate new cell types from somatic cells in vitro and in vivo. Methods: In this study, we established rapid chemically induced platform for transdifferentiation of bovine ear fibroblasts into adipocyte-like cells using a small-molecule cocktail (Repsox, VPA, TTNPB). The chemically induced adipocytes (CiADCs) were characterized by lipid staining, qRT-PCR and WB. Bovine natural adipocytes were used as positive control, and the expression of adipocyte-related marker genes in CiADCs were analyzed. Moreover, RNA-Seq explore the mechanism of RVB in the regulation of Bovine adipocyte transdifferentiation. Results: In this study, the chemically induced adipocytes (CiADCs) could be identified as early as day 6. The CiADCs appeared to be circular and rich of lipid droplets. The adipocyte-specific genes of LPL, PPARγ, IGF1, GPD1, C/EBPδ, ADIPOQ, PCK2, FAS, C/EBPβ, PPARGC1A, C/EBPα, and CFD were detected to be significantly upregulated in both CiADCs and natural adipocytes. Western blot analysis also confirmed the increase C/EBPα and PPARγ protein level in induced adipocytes (CiADCs-6d) treated with RVB. In addition, we also found that the signaling pathways (PPAR signaling pathway, PI3K-Akt signaling pathway, p53 signaling pathway, MAPK signaling pathway, and ECM-receptor interaction) regulated by the DEGs played a vital role in adipogenesis. Discussion: In the present study, a combination of small-molecule compounds RVB was used to transdifferentiate bovine ear fibroblasts into the chemically-induced adipocyte cells (CiADCs) that have a large number of lipid droplets. Importantly, the small-molecule cocktail significantly shortened the reprogramming turnaround time. The morphology of CiADCs is close to the "ring type" of natural differentiated adipocytes on sixth day. And, the CiADCs showed similar adipocyte-specific gene expression patterns to natural adipocytes. Furthermore, RVB increased protein expression of PPARγ and C/EBPα in the chemically-induced adipocytes (CiADCs-6d). Our findings reveal that the signaling pathways of C/EBPα and PPARγ play pivotal roles in this transdifferentiation process. In addition, we also found that the signaling pathways (PPAR signaling pathway, PI3K-Akt signaling pathway, p53 signaling pathway, MAPK signaling pathway, and ECM-receptor interaction) regulated by the DEGs played a vital role in adipogenesis. In general, this study provides valuable evidence to deepen our understanding of the molecular mechanism of small molecule cocktails in regulating adipogenesis.

CTRP6 suppresses neutrophil extracellular traps formation to ameliorate sepsis-induced lung injury through inactivation of ERK pathway

BACKGROUND

Septic lung injury is associated with excessive neutrophil activation, while neutrophil extracellular traps formation contributes to inflammatory lung injury in sepsis. C1q/tumor necrosis factor-related protein-6 (CTRP6) is a paralog of adiponectin and exerts anti- inflammatory and antioxidant properties. The role of CTRP6 in sepsis-associated inflammatory lung injury was investigated in this study.

METHODS

Mice were injected with lipopolysaccharides (LPS) intraperitoneally to establish the mouse sepsis model. They were first tail-vein injected with adenovirus-mediated overexpression CTRP6 (Ad-CTRP6) and then subjected to the LPS injection. Pathological changes in lungs were detected by hematoxylin and eosin staining. Inflammation cytokine levels in bronchoalveolar lavage fluid were assessed by qRT-PCR and ELISA. Flow cytometry was used to detect the number of neutrophils in bronchoalveolar lavage fluid, and immunofluorescence was performed to assess neutrophil extracellular traps.

RESULTS

Lipopolysaccharides induced pulmonary congestion, interstitial edema, and alveolar wall thickening in the lungs, as well as upregulated lung histology score and wet/dry weight ratio. CTRP6 was reduced in lung tissues of septic mice. Injection with Ad-CTRP6 ameliorated extensive histopathological changes in LPS-induced mice and decreased lung histology score and wet/dry weight ratio. Overexpression of CTRP6 reduced the levels of TNF-α, IL-6, and IL-1β in septic mice. Injection with Ad-CTRP6 also decreased the number of neutrophils and downregulated Cit-H3 and myeloperoxidase polymers in septic mice. Protein expression of p-ERK in septic mice was reduced by overexpression of CTRP6.

CONCLUSION

CTRP6 attenuated septic lung injury, exerted anti-inflammatory effect, and suppressed neutrophil extracellular traps formation against sepsis through inactivation of extracellular signal-regulated kinase signaling.

Methylglyoxal Induces Inflammation, Metabolic Modulation and Oxidative Stress in Myoblast Cells

Uremic sarcopenia is a serious clinical problem associated with physical disability and increased morbidity and mortality. Methylglyoxal (MG) is a highly reactive, dicarbonyl uremic toxin that accumulates in the circulatory system in patients with chronic kidney disease (CKD) and is related to the pathology of uremic sarcopenia. The pathophysiology of uremic sarcopenia is multifactorial; however, the details remain unknown. We investigated the mechanisms of MG-induced muscle atrophy using mouse myoblast C2C12 cells, focusing on intracellular metabolism and mitochondrial injury. We found that one of the causative pathological mechanisms of uremic sarcopenia is metabolic flow change to fatty acid synthesis with MG-induced ATP shortage in myoblasts. Evaluation of cell viability revealed that MG showed toxic effects only in myoblast cells, but not in myotube cells. Expression of mRNA or protein analysis revealed that MG induces muscle atrophy, inflammation, fibrosis, and oxidative stress in myoblast cells. Target metabolomics revealed that MG induces metabolic alterations, such as a reduction in tricarboxylic acid cycle metabolites. In addition, MG induces mitochondrial morphological abnormalities in myoblasts. These changes resulted in the reduction of ATP derived from the mitochondria of myoblast cells. Our results indicate that MG is a pathogenic factor in sarcopenia in CKD.

Interleukin-4-induced FABP4 promotes lipogenesis in human skeletal muscle cells by activating the PPAR γ signaling pathway

Chronic low back pain (CLBP) is a common symptom of lumbar degenerative disease. Degeneration of the lumbar paravertebral muscles causes a loss of muscle mass and strength, which is a vital factor causing CLBP and often accompanied by lipid infiltration. Tandem mass spectrometry (TMT) was used to identify differentially expressed proteins in lipid-infiltrated and normal muscles. The results show that fatty acid binding protein 4 (FABP4) participated in the peroxisome proliferator-activated receptor-γ (PPAR γ) signaling pathway as an up-regulated protein, which is related to lipogenesis in diverse cells. In addition, chronic inflammation is believed to be involved in lumbar muscle degeneration and lipogenesis, with interleukin-4 (IL-4) considered as the predominant contributor. In present study, we investigate the effect of FABP4 on lipogenesis in human skeletal muscle cells (HSMCs) stimulated by Interleukin-4 (IL-4) and explore the mechanistic basis. We found expression level of FABP4 in lipid-infiltrated muscles was significantly higher than that in normal muscles. Lipogenesis in HSMCs could be increased by IL-4 treatment, as well as by FABP4 overexpression. FABP4 inhibition suppressed IL-4-mediated lipogenesis in HSMCs, whereas the PPAR γ inhibitor alleviated lipogenesis in both IL-4-treated and FABP4-overexpressed HSMCs. Collectively, the results indicate that FABP4 induces lipogenesis in HSMCs stimulated with IL-4 via activating the PPAR γ signaling pathway. Our study offers a detailed perspective on the pathogenesis of muscle lipid infiltration and provides a potential target for the clinical treatment strategy of muscle lipid infiltration and CLBP.

The CTRP3-AdipoR2 Axis Regulates the Development of Experimental Autoimmune Encephalomyelitis by Suppressing Th17 Cell Differentiation

C1q/TNF-related proteins (CTRP) including CTRP3 are a group of secreted proteins which have a complement C1q-like domain in common, and play versatile roles in lipid metabolism, inflammation, tumor metastasis and bone metabolism. Previously, we showed that the expression of C1qtnf3, encoding CTRP3, is highly augmented in joints of autoimmune arthritis models and CTRP3-deficiency exacerbates collagen-induced arthritis in mice. However, the mechanisms how CTRP3-deficiency exacerbates arthritis still remain to be elucidated. In this study, we showed that CTRP3 was highly expressed in Th17 cell, a key player for the development of autoimmune diseases, and Th17 cell differentiation was augmented in C1qtnf3^–/– mice. Th17 cell differentiation, but not Th1 cell differentiation, was suppressed by CTRP3 and this suppression was abolished by the treatment with a receptor antagonist against AdipoR2, but not AdipoR1, associated with suppression of Rorc and Stat3 expression. Furthermore, AdipoR1 and AdipoR2 agonist, AdipoRon suppressed Th17 cell differentiation via AdipoR2, but not AdipoR1. The development of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis was enhanced in C1qtnf3^–/– mice associated with increase of Th17 cell population. CTRP3 inhibited MOG-induced IL-17 production from T cells by affecting both T cells and dendritic cells. These results show that CTRP3 is an endogenous regulator of Th17 differentiation, suggesting that the CTRP3-AdipoR2 axis is a good target for the treatment of Th17 cell-mediated diseases.

Myostatin suppresses adipogenic differentiation and lipid accumulation by activating crosstalk between ERK1/2 and PKA signaling pathways in porcine subcutaneous preadipocytes

The current study was undertaken to determine the effect of myostatin (MSTN) on lipid accumulation in porcine subcutaneous preadipocytes (PSPAs) and to further explore the potential molecular mechanisms. PSPAs isolated from Meishan weaned piglets were added with various concentrations of MSTN recombinant protein during the entire period of adipogenic differentiation process. Results showed that MSTN treatment significantly reduced the lipid accumulation, intracellular triglyceride (TG) content, glucose consumption and glycerol phosphate dehydrogenase activity, while increased glycerol and free fatty acid release. Consistent with above results, the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway was obviously activated and thus key adipogenic transcription factors peroxisome proliferator-activated receptor-gamma (PPAR-γ), CCAAT/enhancer-binding protein-alpha (C/EBP-α) and their downstream engymes fatty acid synthase and acetyl-CoA carboxylase were all inhibited. However, chemical inhibition of ERK1/2 signaling pathway by PD98059 markedly reversed the decreased TG content by increasing PPAR-γ expression. In addition, MSTN activated the cyclic AMP/protein kinase A (cAMP/PKA) pathway and stimulated lipolysis by reducing the expression of antilipolytic gene perilipin, thus elevated key lipolytic enzymes adipose triglyceride lipase and hormone-sensitive lipase expression and enzyme activity. On the contrary, pretreatment with PKA inhibitor H89 significantly reversed TG accumulation by increasing PPAR-γ expression and thus inhibiting ERK1/2, perilipin and HSL phosphorylation, supporting the crosstalk between PKA and ERK1/2 pathways in both the anti-adipogenic and pro-lipolytic effects. In summary, our results suggested that MSTN suppressed adipogenesis and stimulated lipolysis, which was mainly mediated by activating crosstalk of ERK1/2 and PKA signaling pathways, and consequently decreased lipid accumulation in PSPAs, our findings may provide novel insights for further exploring MSTN as a potent inhibitor of porcine subcutaneous lipid accumulation.

Impact of Conventional and Atypical MAPKs on the Development of Metabolic Diseases

The family of mitogen-activated protein kinases (MAPKs) consists of fourteen members and has been implicated in regulation of virtually all cellular processes. MAPKs are divided into two groups, conventional and atypical MAPKs. Conventional MAPKs are further classified into four sub-families: extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK1, 2 and 3), p38 (α, β, γ, δ), and extracellular signal-regulated kinase 5 (ERK5). Four kinases, extracellular signal-regulated kinase 3, 4, and 7 (ERK3, 4 and 7) as well as Nemo-like kinase (NLK) build a group of atypical MAPKs, which are activated by different upstream mechanisms than conventional MAPKs. Early studies identified JNK1/2 and ERK1/2 as well as p38α as a central mediators of inflammation-evoked insulin resistance. These kinases have been also implicated in the development of obesity and diabetes. Recently, other members of conventional MAPKs emerged as important mediators of liver, skeletal muscle, adipose tissue, and pancreatic β-cell metabolism. Moreover, latest studies indicate that atypical members of MAPK family play a central role in the regulation of adipose tissue function. In this review, we summarize early studies on conventional MAPKs as well as recent findings implicating previously ignored members of the MAPK family. Finally, we discuss the therapeutic potential of drugs targeting specific members of the MAPK family.

Knockdown of CTRP6 reduces the deposition of intramuscular and subcutaneous fat in pigs via different signaling pathways

The regulation of porcine subcutaneous (SC) and intramuscular (IM) fat deposition significantly affects pork quality and the lean meat percentage of the carcass, respectively. The adipokine C1q/tumor necrosis factor-related protein 6 (CTRP6), plays a significant role in regulating animal fat deposition. The purpose of this study was to understand the effects of CTRP6 gene knockdown in IM and SC adipocytes by RNA-seq analysis. A total of 1830 and 2936 differentially expressed genes (DEGs) were identified in SC and IM adipocytes, respectively. 844 were down- and 2092 were upregulated in SC adipocytes, while 648 were down- and 1182 were upregulated in IM adipocytes. Furthermore, 1778 DEGs were detected only in SC adipocytes, 672 DEGs only in IM adipocytes, and 1158 DEGs in both types of adipocytes. GO analysis indicated that DEGs involved in adipocyte differentiation were significantly enriched in both SC and IM adipocytes following treatment with CTRP6-siRNA. Moreover, KEGG pathway enrichment analysis revealed differences of metabolic regulation between IM and SC adipocytes. With CTRP6-silencing, the signaling pathways related to Ras and arachidonic acid metabolism were significantly enriched in IM adipocytes, while four other signaling pathways, encompassing the TNF, MAPK, p53 and adipokine pathway were specifically enriched in SC adipocytes. Interestingly, the effect of CTRP6-siRNA treatment was attenuated by the specific Ras activator ML-097 in IM adipocytes, while the specific p53 activator SJ-172550 had the corresponding effect in SC adipocytes. Altogether, we suggest that CTRP6 may be a differential regulator of the development and metabolism of IM and SC adipose tissues.

Differential Regulatory Roles of MicroRNAs in Porcine Intramuscular and Subcutaneous Adipocytes

The deposition of intramuscular (IM) and subcutaneous (SC) fat is an important trait influencing pork quality. Understanding the genetic differences between these two types of adipose tissues is consequently of great importance for pig breeding. Here, we established primary cultures of IM and SC adipocytes from Jiaxing black pigs. The microRNA (miRNA) expression profiles of the two types of adipocytes were obtained by RNA-seq. A total of 741 miRNAs were identified in IM and SC adipocytes, including 155 significant differentially expressed (SDE) miRNAs. According to gene ontology and Kyoto Encyclopedia of Genes analysis, the target genes of the SDE miRNAs were enriched in categories and pathways related to transcriptional regulation, fatty acid biosynthesis, as well as the MAPK and PI3K/Akt pathways. Notably, miR-206 expression was 36-fold higher in IM adipocytes than in SC adipocytes. The overexpression of miR-206 in IM and SC adipocytes decreased cell proliferation and triglyceride accumulation. Luciferase activity assays and quantitative polymerase chain reaction confirmed that miR-206 regulates adipocyte proliferation by targeting STARD7 and inhibits adipogenesis by repressing Krüppel-like factor 4 (KLF4) expression. Accordingly, the effect of miR-206 mimics was attenuated by the overexpression of KLF4 in adipocytes. Taken together, we identified the expression profiles of miRNAs in adipocytes, which revealed that miR-206 acts as a suppressor of adipogenesis.

C1q/TNF-Related Protein 6 Is a Pattern Recognition Molecule That Recruits Collectin-11 from the Complement System to Ligands

C1q/TNF-related protein (CTRP) 6 is a member of the CTRP protein family associated with the regulation of cellular and endocrine processes. CTRP6 contains collagen and globular structures, resembling the pattern recognition molecules (PRMs) of the classical and lectin complement pathways. We expressed human CTRP6 in Chinese hamster ovary cells and investigated the binding to different putative ligands (acetylated BSA [AcBSA], zymosan, mannan, and LPS from Escherichia coli and Salmonella as well as to the monosaccharides l-fucose, d-mannose, N-acetylglucosamine, N-acetylgalactosamine, and galactose). Furthermore, we investigated the binding of CTRP6 to various Gram-negative bacteria as well as PRMs and enzymes of the lectin complement pathway. We found that CTRP6 bound to AcBSA and to a lesser extent to zymosan. Using EDTA as chelating agent, we observed an increased binding to AcBSA, zymosan and the two strains of LPS. We detected no binding to mannan and BSA. We identified l-fucose as a ligand for CTRP6 and that it bound to certain enteroaggregative Escherichia coli and Pseudomonas aeruginosa isolates, whereas to other bacterial isolates, no binding was observed. CTRP6 did not appear to interact directly with the activating enzymes of the lectin pathway; however, we could show the specific recruitment of collectin-11 and subsequent initiation of the complement cascade through deposition of C4. In conclusion, our results demonstrate the binding of CTRP6 to a variety of microbial and endogenous ligands identifying CTRP6 as a novel human lectin and PRM of importance for complement recognition and innate immunity.

Circulating levels of C1q/TNF-α-related protein 6 (CTRP6) in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders affecting females of reproductive age. It has been associated with cardiometabolic disorders including diabetes mellitus and cardiovascular disorders, and increases the risk of developing fecundity pathologies including recurrent pregnancy loss (RPL) and infertility. C1q/tumor necrosis factor-α-related protein-6 (CTRP6) is a novel adipokine involved in glucose and lipid metabolism, host inflammation, and organogenesis. In the present study, we aimed to determine the association of serum CTRP6 levels with some components of metabolic syndrome in PCOS patients (infertile PCOS [inf-PCOS] and PCOS-RPL). This case-control study included 120 PCOS patients (60 inf-PCOS and 60 PCOS-RPL) and 60 healthy controls. Serum high-sensitivity C-reactive protein (hs-CRP) and homocysteine were measured using commercial kits, while adiponectin and CTRP6 levels were assessed using ELISA technique. Inf-PCOS and PCOS-RPL individuals had higher levels of serum CTRP6 than controls (546.15 ± 125.02 ng/ml and 534.04 ± 144.19 ng/ml vs. 440.16 ± 159.24 ng/ml; both p < .001). Moreover, serum adiponectin levels were significantly reduced, while fasting insulin, homeostasis model assessment of insulin resistance, free testosterone, and hs-CRP levels were significantly elevated in PCOS group, when compared with controls. Furthermore, serum CTRP6 positively associated with body mass index in all subjects. It showed an inverse correlation with adiponectin in PCOS group and subgroups. However, it had a direct association with hs-CRP in PCOS group and inf-PCOS subgroup, but not PCOS-RPL subgroup. These findings unravel a probable role of CTRP6 in PCOS pathogenesis, which poses a possibility to be a good diagnostic target. However, further investigation is needed.

Adipose-Tissue-Specific Expression of Pig ApoR Protects Mice from Diet-Induced Obesity

Fat deposition is one of the most important economic traits of pigs. Decreasing the subcutaneous fat and increasing the intramuscular fat are believed to be an effective way to improve pork quality, which is one of the main goals of pig breeding. Identifying key genes that control porcine lipid metabolism is essential for achieving this goal. Apolipoprotein R (apoR) was identified as the crucial molecule in the process of pig adipose reduction by clenbuterol. In this study, transgenic mice with adipose-tissue-specific overexpression of pig apoR (apoR mice) were constructed. The apoR mice gained less weight than wild-type (WT) mice after 18 weeks of feeding a high-fat diet. A comparison of organs between the two genotypes revealed that the weight of white adipose tissue, including inguinal and epididymal fat tissue, was significantly decreased and the weight of liver tissue was increased in apoR mice compared with WT mice. Glucose and insulin intolerance tests showed that the glucose metabolism of apoR mice was similar to that of WT mice. Histological staining proved that the adipocytes of apoR mice had a reduced average size, and gene expression analysis indicated that lipolysis in the adipose tissue of apoR mice was enhanced. Finally, the primary culture of inguinal adipocytes revealed that apoR promotes lipolysis via the Erk1/2 pathway. Taken together, the results indicate that adipose-tissue-specific expression of pig apoR protects mice from diet-induced obesity by enhancing lipolysis.

LncRNA SNHG16 induces the SREBP2 to promote lipogenesis and enhance the progression of pancreatic cancer

Aim: Blocking lipogenesis could significantly inhibit the progression of pancreatic cancer. Exploring the regulatory mechanisms of lipogenesis by lncRNA SNHG16 might be of great significance to control the development of pancreatic cancer. Methods: The proliferation, migration, invasion and lipogenesis were determined with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, wound healing, transwell and Oil Red O staining assays, respectively. The interactions among lncRNA SNHG16, miR-195 and SREBP2 were analyzed by dual luciferase reporter assays. Results: Both the knock down of lncRNA SNHG16 and SREBP2 and overexpression of miR-195 suppressed the proliferation, migration, invasion and lipogenesis in pancreatic cancer cells. LncRNA SNHG16 directly sponged miR-195 to modulate the lipogenesis via regulating the expression of SREBP2. Conclusion: LncRNA SNHG16 accelerated the development of pancreatic cancer and promoted lipogenesis via directly regulating miR-195/SREBP2 axis.

Circulating CTRP6 Levels are Increased in Overweight or Obese Chinese Individuals and Associated with Insulin Resistance Parameters: A Pilot Study

AIMS

CTRP6, a newly discovered adipokine, has been found to be a regulator for energy homeostasis. However, the association between circulating CTRP6 and obesity in humans is still unclear.

METHODS

256 individuals, including 185 overweight/obese (OW/OB) and 71 normal weight adults, were recruited for this study. Circulating concentrations of CTRP6 and adiponectin (Adipoq) were examined by ELISA.

RESULTS

Serum CTRP6 levels in obese individuals were significantly increased compared with those in healthy individuals (506.1±134.9 vs.363.3±80.5 ng/mL, P<0.01). Conversely, serum Adipoq concentrations in OW/OB individuals were markedly decreased compared with healthy controls [20.8 (12.1-29.3) vs. 14.1 ⁽ 8.61-17.7) ^; P<0.01]. Correlation analysis revealed that there was a positive relationship between circulating CTRP6 and age, BMI, Fat%, LDL-C, TG, WHR, TC, FBG, FIns, HOMA-IR and HbA1c, but there was an inverse correlation with Adipoq and HDL-C. Logistic regression analysis revealed that high serum CTRP6 levels are markedly associated with OW/OB. Finally, ROC curve analysis showed that the cut-off value for serum CTRP6 for prediction of IR is 518 ng/mL.

CONCLUSIONS

CTRP6 may be a marker related to OW/OB.

C1QTNF6 as a novel biomarker regulates cellular behaviors in A549 cells and exacerbates the outcome of lung adenocarcinoma patients

C1q/tumor necrosis factor-related protein 6 (C1QTNF6) is a member of the CTRP family and implicated to cardiovascular diseases, inflammatory reaction, and adipogenesis. However, the function of C1QTNF6 in lung adenocarcinoma remains unknown. We downloaded the expression profiles of C1QTNF6 from TCGA database and Oncomine dataset in order to analyze the relationship between C1QTNF6 expression level and tumorigenesis by bioinformatics methods, such as chi-square test, Kaplan-Meier, and Cox regression analysis. In addition, we performed experiments to investigate the biological function of C1QTNF6 on cancer cells in vitro. The siRNA strategy was conducted to decrease the C1QTNF6 expression and then Cell Counting Kit-8 (CCK8) assay and wound-healing and transwell assays were to determine the proliferation, migration, and invasion. Western blot and qRT-PCR were used to confirm the expression levels. Based on the TCGA database and Oncomine dataset, we found that C1QTNF6 was over expressed in lung adenocarcinoma. The statistical data also showed that the high-regulated C1QTNF6 was related to poor prognosis in patients with lung adenocarcinoma. Moreover, the capabilities of proliferation, migration, and invasion were inhibited owing to the knockdown of C1QTNF6 in lung adenocarcinoma cells. And the phosphorylation of MEK and ERK was blocked by treated si-C1QTNF6 compared with the GAPDH. In conclusion, aberrant C1QTNF6 expression was implicated in terrible prognosis accompanying with the damage of relevant cell potential in lung adenocarcinoma. C1QTNF6 might be an independent predictor of prognosis in lung adenocarcinoma.

Comprehensive transcriptomic view of the role of the LGALS12 gene in porcine subcutaneous and intramuscular adipocytes

Background

Livestock production aims to provide meats of high and consistent eating quality. Insufficient intramuscular (IM) fat and excessive subcutaneous (SC) fat are paramount pork quality challenges. IM fat and SC fat, which are modulated by the adipogenesis of IM and SC adipocytes, play key roles in pork quality. Galectin-12 (LGALS12) was proven to be an important regulator of fat deposition in porcine. However, the current knowledge of the transcriptome-wide role of LGALS12 in adipocytes is still limited. This study was aimed to discover the different regulatory mechanisms of LGALS12 in porcine IM and SC adipocyte.

Results

The siRNA-mediated knockdown of the expression of LGALS12 identified 1075 and 3016 differentially expressed genes (DEGs) in IM and SC adipocytes, respectively. Among these, 585 were up- and 490 were downregulated in the IM adipocytes, while 2186 were up- and 830 were downregulated in the SC adipocytes. Moreover, 418 DGEs were observed only in the IM adipocytes, 2359 DGEs only in the SC adipocytes, and 657 DGEs in both types of adipocytes. According to Gene Ontology (GO) analysis, DEGs in both IM and SC adipocytes were mainly enriched in categories related to lipids or fat cell differentiation. Pathway analysis of the DEGs revealed 88 changed signaling pathways in the IM adipocytes and 86 in the SC adipocytes. The signaling pathways present in only one type of adipocyte were identified from among the top 50 signaling pathways in each type of adipocyte. Four signaling pathways, encompassing PI3K-AKT, cardiac muscle contraction, fatty acid metabolism and Ras, were significantly enriched in the IM adipocytes. On the other hand, four different signaling pathways, encompassing TNF, WNT, cGMP-PKG and NF-kappa B, were greatly enriched in the SC ones. The pathway changes were confirmed by chemical inhibition assays.

Conclusions

Our data reveals that LGALS12 knockdown alters the expression of numerous genes involved in key biological processes in the development of adipocytes. These observations provide a global view of the role of LGALS12 in porcine IM and SC adipocytes; thus, improving our understanding of the regulatory mechanisms by which this gene acts in fat development.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5891-y) contains supplementary material, which is available to authorized users.

C1q/TNF-related protein-6 is associated with insulin resistance and the development of diabetes in Chinese population

AIMS

C1q/tumor necrosis factor-related protein-6 (CTRP6) is a novel adipokine and has emerged as an important mediator for lipid and glucose metabolism. However, to date, the relationship between CTRP6 and T2DM in humans has not been demonstrated. Our objective is to investigate the association of circulating CTRP6 with T2DM in a cross-sectional study.

METHODS

118 patients with newly diagnosed T2DM, 98 subjects with impaired glucose tolerant (IGT) and 132 healthy subjects were recruited for this study. OGTT were performed in 48 healthy individuals to investigate the association of CTRP6 with glucose, insulin and other adipokines. Circulating CTRP6, TNF-α and Adipoq were measured by ELISA.

RESULTS

IGT and T2DM individuals had higher serum CTRP6 levels than healthy controls (406.2 ± 136.6 and 539.1 ± 169.7 vs. 354.3 ± 117.2 ng/mL; both P < 0.01), whereas serum CTRP6 concentrations were further increased in T2DM patients compared with IGT individuals (P < 0.01). Serum CTRP6 levels were found to be related positively to BMI, WHR, FAT%, TC, TG, HbA1c, FBG, 2 h-OGTT, fasting insulin (FIns), 2 h-Ins, HOMA-IR and TNF-α, and negatively with HDL-C and Adipoq in all individuals (P < 0.05 or P < 0.01). Multivariate logistic regression analysis demonstrated that CTRP6 was correlated with both IGT and T2DM. After an oral glucose challenge, serum CTRP6 concentrations exhibited a similar change with blood glucose, insulin, TNF-α and Adipoq.

CONCLUSIONS

CTRP6 may be a metabolism- and nutrition-related adipokine and may be related to insulin resistance and T2DM.

TRIAL REGISTRATIONS

Clinical Trial Registration Number: ChiCTR-OCC-11001422. Registration name: Plasma cytokines and endothelial function in type 2 diabetes.

Knockdown of LGALS12 inhibits porcine adipocyte adipogenesis via PKA-Erk1/2 signaling pathway

Increasing intramuscular (IM) fat while concomitantly decreasing subcutaneous (SC) fat content is one major goal of pig breeding. Identifying genes involved in lipid metabolism is critical for this goal. Galectin-12 (LGALS12) has been proven to be an important regulator of fat deposition in mouse models; however, the effect and regulatory mechanisms of LGALS12 on porcine adipogenesis are still unknown. In this study, the effects of LGALS12 on fat deposition were explored with primary culture of porcine SC and IM adipocytes. Analysis of LGALS12 expression across different tissues revealed that LGALS12 was predominantly expressed in adipose tissue. The LGALS12 expression patterns across stages of adipocyte differentiation were also evaluated, with differences observed between SC and IM fat. Small interfering RNA (siRNA) of LGALS12 was designed and transfected into porcine adipocytes derived from SC and IM fat. After transfection, the expression level of LGALS12 was significantly reduced, and the number of lipid droplets was reduced in adipocytes from both SC and IM fat. Simultaneously, the levels of adipogenic markers, including PPARγ and aP2, were decreased, whereas hydrolysis markers, including adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), were increased. Furthermore, the activation of lipolysis signals, such as the phosphorylation of PKA and Erk1/2, were observed with LGALS12 knockdown in terminally differentiated adipocytes from both SC and IM sources. Taken together, these results suggest that LGALS12 knockdown can inhibit adipogenesis of porcine adipocytes by downregulating lipogenic genes and activating the PKA-Erk1/2 signaling pathway.

Betaine promotes lipid accumulation in adipogenic-differentiated skeletal muscle cells through ERK/PPARγ signalling pathway

Betaine, a neutral zwitterionic compound, could regulate intramuscular fat (IMF) deposition and meat quality. However, the efficacy is controversial. Moreover, the regulatory mechanism of betaine on lipid metabolism in skeletal muscle cells remains unclear. Therefore, in this study, we examined the effects and regulatory mechanism of betaine on lipid accumulation in adipogenic-differentiated C2C12 cells. We found that adipogenic-induced C2C12 cells treated with 10 mM betaine for 24 and 48 h had more lipid accumulation than the control group. Real-time PCR and Western blot results revealed that betaine treatment did not alter the expression of lipolysis and lipid oxidation-related genes, but dramatically increased the expression of peroxisome proliferator-activated receptor γ (PPARγ) and its target genes such as fatty acid binding protein 4 (aP2), fatty acid synthase (FAS) and lipoprteinlipase (LPL). Furthermore, betaine combined with PPARγ inhibitor GW9662 treatment showed that betaine elevated C2C12 lipid accumulation through upregulation of PPARγ. Mechanistically, we found that betaine promoted PPARγ expression and lipid accumulation through inhibition of extracellular regulated protein kinases1/2 (ERK1/2) signalling pathway. These results demonstrate that betaine acts through ERK1/2-PPARγ signalling pathway to regulate lipid metabolism in adipogenic-differentiated skeletal muscle cells, which could provide some useful information for controlling muscle lipid accumulation by manipulating ERK1/2 and PPARγ signalling pathway.

CTRP6 Regulates Porcine Adipocyte Proliferation and Differentiation by the AdipoR1/MAPK Signaling Pathway

Intramuscular fat (IMF) and subcutaneous fat (SCF), which are modulated by adipogenesis of intramuscular and subcutaneous adipocytes, play key roles in pork quality. C1q/tumor necrosis factor-related protein 6 (CTRP6), an adipokine, plays an important role in the differentiation of 3T3-L1 cells. However, the effect and regulatory mechanisms of CTRP6 on porcine adipogenesis, and whether CTRP6 has the same effect on intramuscular and subcutaneous adipocytes, are still unknown. Here, we found that CTRP6 significantly inhibited both adipocyte proliferation assessed by proliferative marker expression, but CTRP6 decreased the proliferation rate of intramuscular adipocytes (IM) to a greater extent than subcutaneous adipocytes (SC). Moreover, CTRP6 promoted the activity of the p38 signaling pathway during the proliferation of both cell types. Nevertheless, in subcutaneous adipocytes, CTRP6 also influenced the phosphorylation of extracellular regulated protein kinases1/2 (p-Erk1/2), but not in intramuscular adipocytes. Additionally, during the differentiation of intramuscular and subcutaneous adipocytes, CTRP6 increased adipogenic genes expression and the level of p-p38, while it decreased the activity of p-Erk1/2. Interestingly, the effect of CTRP6 shRNA or CTRP6 recombinant protein was attenuated by U0126 (a special p-Erk inhibitor) or SB203580 (a special p-p38 inhibitor) in adipocytes. By target gene prediction and experimental validation, we demonstrated that CTRP6 may be a target of miR-29a in porcine adipocytes. Moreover, AdipoR1was identified as a receptor of CTRP6 in intramuscular adipocytes, but not in subcutaneous adipocytes. On the basis of the above findings, we suggest that CTRP6 was the target gene of miR-29a, inhibited intramuscular and subcutaneous adipocyte proliferation, but promoted differentiation by the mitogen-activated protein kinase (MAPK) signaling pathway. These findings indicate that CTRP6 played an essentially regulatory role in fat development.

C1q/tumor necrosis factor-related protein-3 enhances the contractility of cardiomyocyte by increasing calcium sensitivity

C1q/tumor necrosis factor-related protein-3 (CTRP3) is an adipokine that protects against myocardial infarction-induced cardiac dysfunction through its pro-angiogenic, anti-apoptotic, and anti-fibrotic effects. However, whether CTRP3 can directly affect the systolic and diastolic function of cardiomyocytes remains unknown. Adult rat cardiomyocytes were isolated and loaded with Fura-2AM. The contraction and Ca²⁺ transient data was collected and analyzed by IonOptix system. 1 and 2μg/ml CTRP3 significantly increased the contraction of cardiomyocytes. However, CTRP3 did not alter the diastolic Ca²⁺ content, systolic Ca²⁺ content, Ca²⁺ transient amplitude, and L-type Ca²⁺ channel current. To reveal whether CTRP3 affects the Ca²⁺ sensitivity of cardiomyocytes, the typical phase-plane diagrams of sarcomere length vs. Fura-2 ratio was performed. We observed a left-ward shifting of the late relaxation trajectory after CTRP3 perfusion, as quantified by decreased Ca²⁺ content at 50% sarcomere relaxation, and increased mean gradient (μm/Fura-2 ratio) during 500-600ms (-0.163 vs. -0.279), 500-700ms (-0.159 vs. -0.248), and 500-800ms (-0.148 vs. -0.243). Consistently, the phosphorylation level of cardiac troponin I at Ser23/24 was reduced by CTRP3, which could be eliminated by preincubation of okadaic acid, a type 2A protein phosphatase inhibitor. In summary, CTRP3 increases the contraction of cardiomyocytes by increasing the myofilament Ca²⁺ sensitivity. CTRP3 might be a potential endogenous Ca²⁺ sensitizer that modulates the contractility of cardiomyocytes.