Reduced serum CLCF1 levels in hyperthyroidism patients and T3-treated mice.

Characteristic symptoms of hyperthyroidism include weight loss, heart palpitation, and sweating. Thyroid hormones (TH) can stimulate thermogenesis through central and peripheral mechanisms. Previous studies have shown an association between dysfunction of cardiotrophin-like cytokine factor 1 (CLCF1) and cold-induced sweating syndrome, with recent research also indicating a link between CLCF1 and brown adipose tissue thermogenesis. However, it remains unclear whether CLCF1 and TH have synergistic or antagonistic effects on thermogenesis. This study aims to investigate the influence of thyroid hormone on circulating CLCF1 levels in humans and explore the potential possibilities of thyroid hormone in regulating energy metabolism by modulating Clcf1 in mice. By recruiting hyperthyroid patients and healthy subjects, we observed significantly lower serum CLCF1 levels in hyperthyroid patients compared to healthy subjects, with serum CLCF1 levels independently associated with hyperthyroidism after adjusting for potential confounders. Tissue analysis from mice treated with T3 revealed a decrease in CLCF1 expression in BAT and iWAT of C57BL/6 mice. These findings suggest that TH may play a role in regulating CLCF1 expression in adipose tissue.

CLCF1 signaling restrains thermogenesis and disrupts metabolic homeostasis by inhibiting mitochondrial biogenesis in brown adipocytes.

Great progress has been made in identifying positive regulators that activate adipocyte thermogenesis, but negative regulatory signaling of thermogenesis remains poorly understood. Here, we found that cardiotrophin-like cytokine factor 1 (CLCF1) signaling led to loss of brown fat identity, which impaired thermogenic capacity. CLCF1 levels decreased during thermogenic stimulation but were considerably increased in obesity. Adipocyte-specific CLCF1 transgenic (CLCF1-ATG) mice showed impaired energy expenditure and severe cold intolerance. Elevated CLCF1 triggered whitening of brown adipose tissue by suppressing mitochondrial biogenesis. Mechanistically, CLCF1 bound and activated ciliary neurotrophic factor receptor (CNTFR) and augmented signal transducer and activator of transcription 3 (STAT3) signaling. STAT3 transcriptionally inhibited both peroxisome proliferator-activated receptor-γ coactivator (PGC) 1α and 1ß, which thereafter restrained mitochondrial biogenesis in adipocytes. Inhibition of CNTFR or STAT3 could diminish the inhibitory effects of CLCF1 on mitochondrial biogenesis and thermogenesis. As a result, CLCF1-TG mice were predisposed to develop metabolic dysfunction even without external metabolic stress. Our findings revealed a brake signal on nonshivering thermogenesis and suggested that targeting this pathway could be used to restore brown fat activity and systemic metabolic homeostasis in obesity.

Bromodomain-containing protein 4 activates cardiotrophin-like cytokine factor 1, an unfavorable prognostic biomarker, and promotes glioblastoma in vitro.

Background: Glioblastoma (GBM) is one of the most common and malignant brain tumors. Cardiotrophin-like cytokine factor 1 (CLCF1) is a member of the IL-6 superfamily. However, the clinical significance, potential role, and molecular mechanism of CLCF1 in GBM remain obscure. Here, the expression and prognostic significance of CLCF1 was investigated in GBM. Methods: The Cancer Genome Atlas (TCGA) GBM and Chinese Glioma Genome Atlas (CGGA) datasets were downloaded and analyzed by using Gene Expression Profiling Interactive Analysis (GEPIA). Next, 3 shRNAs targeting CLCF1 were designed, and silencing efficiency was examined with real-time polymerase chain reaction (PCR). Cell Counting Kit 8 (CCK-8), flow cytometry, transwell, and wound healing assays were used to study the function of CLCF1 in glioma cells. Results: We found increased expression of CLCF1 as an unfavorable prognostic marker in GBM. Functionally, down-regulation of CLCF1 significantly reduced cell proliferation, induced cell apoptosis and cell cycle G2 phase arrest, and weakened the migration and invasion of GBM cells. Downstream pathway analysis was conducted, and potential targets in cytokine receptors, extracellular matrix (ECM) receptors, apoptosis, and the cell cycle were uncovered. Finally, transcriptional regulators were analyzed, and bromodomain-containing protein 4 (BRD4) was found to activate CLCF1 in GBM. Conclusions: CLCF1, transcriptionally activated by BRD4, promotes glioma and serves as an unfavorable marker in GBM.

CLCF1 is up-regulated in renal ischemia reperfusion injury and may associate with FOXO3.

Background: Ischemia-reperfusion injury (IRI) is one of the most important risk factors for acute kidney injury. In kidney transplantation, renal IRI can induce delayed graft function (DGF). However, the mechanisms that link IRI to DGF remain unclear. This study aimed to find molecular markers of renal IRI which are also associated with DGF. Methods: A previously constructed database of differentially expressed genes in a murine IRI model was compared with a published DGF database. The expression of cardiotrophin-like cytokine factor 1 (CLCF1) was detected using immunohistochemistry (IHC) and real-time quantitative polymerase chain reaction (qPCR) assays. Serum CLCF1 was measured using an enzyme-linked immunosorbent assay (ELISA), and serum creatinine (Cr) was tested to evaluate kidney function. Results: By comparing the IRI database and the DGF database, we identified 107 differentially expressed genes, including 79 upregulated and 28 downregulated genes. CLCF1 was one of the upregulated genes found in the 2 databases. The levels of CLCF1 in IRI-treated kidney tissues and serum CLCF1 were upregulated compared to sham-operated mice. CLCF1 belongs to the interleukin-6 (IL-6) family, and the forkhead box O3 (FOXO3) gene plays a key role in regulating IL-6 expression. We observed that FOXO3 knockout induced an increase in serum CLCF1 levels in sham-operated mice. However, FOXO3 knockout failed to increase CLCF1 levels in IRI-treated mice. Conclusions: CLCF1 is upregulated in renal IRI and may be regulated by FOXO3. Our data indicated that CLCF1 might be a potential biomarker linking renal IRI to DGF in kidney transplantation.

Specific cytokines of interleukin-6 family interact with S100 proteins.

Cytokines of interleukin-6 (IL-6) family are important signaling proteins involved in various physiological and pathological processes. Earlier, we described interactions between IL-11 and S100P/B proteins from the family of S100 proteins engaged in the pathogenesis of numerous diseases. We probed here interactions between seven IL-6 family cytokines (IL-6, IL-11, OSM, LIF, CNTF, CT-1, and CLCF1) and fourteen S100 proteins (S100A1/A4/A6/A7/A8/A9/A10/A11/A12/A13/A14/A15/B/P). Surface plasmon resonance spectroscopy revealed formation of calcium-dependent complexes between IL-11, OSM, CNTF, CT-1, and CLCF1 and distinct subsets of S100A1/A6/B/P proteins with equilibrium dissociation constants of 19 nM - 12 µM. The existence of a network of interactions between Ca2+-loaded S100 proteins and IL-6 family cytokines suggest regulation of these cytokines by the extracellular forms of S100 proteins.

Association of cardiotrophin-like cytokine factor 1 levels in peripheral blood mononuclear cells with bone mineral density and osteoporosis in postmenopausal women.

BACKGROUND: Recent research has suggested that cardiotrophin-like cytokine factor 1 (CLCF1) may be an important regulator of bone homeostasis. Furthermore, a whole gene chip analysis suggested that the expression levels of CLCF1 in the peripheral blood mononuclear cells (PBMCs) were downregulated in postmenopausal women with osteoporosis. This study aimed to assess whether the expression levels of CLCF1 in PBMCs can reflect the severity of bone mass loss and the related fracture risk. METHODS: In all, 360 postmenopausal women, aged 50 to 80 years, were included in the study. A survey to evaluate the participants' health status, measurement of bone mineral density (BMD), routine blood test, and CLCF1 expression level test were performed. RESULTS: Based on the participants' bone health, 27 (7.5%), 165 (45.83%), and 168 (46.67%) participants were divided into the normal, osteopenia, and osteoporosis groups, respectively. CLCF1 protein levels in the normal and osteopenia groups were higher than those in the osteoporosis group. While the CLCF1 mRNA level was positively associated with the BMD of total femur (r = 0.169, p = 0.011) and lumbar spine (r = 0.176, p = 0.001), the protein level was positively associated with the BMD of the lumbar spine (r = 0.261, p < 0.001), femoral neck (r = 0.236, p = 0.001), greater trochanter (r = 0.228, p = 0.001), and Ward's triangle (r = 0.149, p = 0.036). Both the mRNA and protein levels were negatively associated with osteoporosis development (r = - 0.085, p = 0.011 and r = - 0.173, p = 0.014, respectively). The association between CLCF1 protein level and fracture risk was not significant after adjusting for BMD. CONCLUSIONS: To our knowledge, this is the first clinical study to show that CLCF1 expression levels in the PBMCs of postmenopausal women can reflect the amount of bone mass or the severity of bone mass loss.

Cardiotrophin-Like Cytokine Factor 1 Exhibits a Myeloid-Biased Hematopoietic-Stimulating Function.

Cardiotrophin-like cytokine factor 1 (CLCF1) is secreted as a complex with the cytokine receptor-like factor 1 (CRLF1). Syndromes caused by mutations in the genes encoding CLCF1 or CRLF1 suggest an important role for CLCF1 in the development and regulation of the immune system. In mice, CLCF1 induces B-cell expansion, enhances humoral responses and triggers autoimmunity. Interestingly, inactivation of CRLF1, which impedes CLCF1 secretion, leads to a marked reduction in the number of bone marrow (BM) progenitor cells, while mice heterozygous for CLCF1 display a significant decrease in their circulating leukocytes. We therefore hypothesized that CLCF1 might be implicated in the regulation of hematopoiesis. To test this hypothesis, murine hematopoietic progenitor cells defined as Lin-Sca1+c-kit+ (LSK) were treated in vitro with ascending doses of CLCF1. The frequency and counts of LSK cells were significantly increased in the presence of CLCF1, which may be mediated by several CLCF1-induced soluble factors including IL-6, G-CSF, IL-1ß, IL-10, and VEGF. CLCF1 administration to non-diseased C57BL/6 mice resulted in a pronounced increase in circulating myeloid cells, which was concomitant with augmented LSK and myeloid cell counts in the BM. Likewise, CLCF1 administration to mice following sub-lethal irradiation or congeneic BM transplantation (BMT) resulted in accelerated LSK recovery along with a sustained increase in BM-derived CD11b+ cells. Altogether, our observations establish an important and unforeseen role for CLCF1 in regulating hematopoiesis with a bias toward myeloid cell differentiation.

Role of cytokine receptor-like factor 1 in hepatic stellate cells and fibrosis.

AIM: To elucidate the role of cytokine receptor-like factor 1 (CRLF1) in hepatic stellate cells and liver fibrosis. METHODS: Rat hepatic stellate cells (HSCs) were isolated by Nykodenz gradient centrifugation and activated by culturing in vitro. Differentially expressed genes in quiescent and culture activated HSCs were identified using microarrays. Injections of carbon tetrachloride (CCl(4)) for 4 wk were employed to induce liver fibrosis. The degree of fibrosis was assessed by Sirius red staining. Adenovirus expressing CRLF1 was injected through tail vein into mice to achieve overexpression of CRLF1 in the liver. The same adenovirus was used to overexpress CRLF1 in quiescent HSCs cultured in vitro. Expression of CRLF1, CLCF1 and ciliary neurotrophic factor receptor (CNTFR) in hepatic stellate cells and fibrotic livers was analyzed by semi-quantitative reverse transcription-polymerase chain reaction and Western blotting. Expression of profibrotic cytokines and collagens was analyzed by the same method. RESULTS: CRLF1 is a secreted cytokine with unknown function. Human mutations suggested a role in development of autonomous nervous system and a role of CRLF1 in immune response was implied by its similarity to interleukin (IL)-6. Here we show that expression of CRLF1 was undetectable in quiescent HSCs and was highly upregulated in activated HSCs. Likewise, expression of CRLF1 was very low in normal livers, but was highly upregulated in fibrotic livers, where its expression correlated with the degree of fibrosis. A cofactor of CLRF1, cardiotrophin-like cytokine factor 1 (CLCF1), and the receptor which binds CRLF1/CLCF1 dimer, the CNTFR, were expressed to similar levels in quiescent and activated HSCs and in normal and fibrotic livers, indicating a constitutive expression. Overexpression of CLRF1 alone in the normal liver did not stimulate expression of profibrotic cytokines, suggesting that the factor itself is not pro-inflammatory. Ectopic expression in quiescent HSCs, however, retarded their activation into myofibroblasts and specifically decreased expression of type III collagen. Inhibition of type III collagen expression by CRLF1 was also seen in the whole liver. Our results suggest that CLRF1 is the only component of the CRLF1/CLCF1/CNTFR signaling system that is inducible by a profibrotic stimulus and that activation of this system by CLRF1 may regulate expression of type III collagen in fibrosis. CONCLUSION: By regulating activation of HSCs and expression of type III collagen, CRLF1 may have an ability to change the composition of extracellular matrix in fibrosis.