Myeloid-derived growth factor alleviates non-alcoholic fatty liver disease alleviates in a manner involving IKKβ/NF-κB signaling

Is myeloid-derived growth factor a ligand of the sphingosine-1-phosphate receptor 2?

Secretory myeloid-derived growth factor (MYDGF) exerts beneficial effects on organ repair, probably via a plasma membrane receptor; however, the identity of the expected receptor has remained elusive. In a recent study, MYDGF was reported as an agonist of the sphingosine-1-phosphate receptor 2 (S1PR2), an A-class G protein-coupled receptor that mediates the functions of the signaling lipid, sphingosine-1-phosphate (S1P). In the present study, we conducted living cell-based functional assays to test whether S1PR2 is a receptor for MYDGF. In the NanoLuc Binary Technology (NanoBiT)-based β-arrestin recruitment assay and the cAMP-response element (CRE)-controlled NanoLuc reporter assay, S1P could efficiently activate human S1PR2 overexpressed in human embryonic kidney (HEK) 293T cells; however, recombinant human MYDGF, overexpressed either from Escherichia coli or HEK293 cells, had no detectable effect. Thus, the results demonstrated that human MYDGF is not a ligand of human S1PR2. Considering the high conservation of MYDGF and S1PR2 in evolution, MYDGF is also probably not a ligand of S1PR2 in other vertebrates.

Myeloid-derived growth factor and its effects on cardiovascular and metabolic diseases

Myeloid-derived growth factor (MYDGF) is a paracrine protein produced by bone marrow-derived monocytes and macrophages. Current research shows that it has protective effects on the cardiovascular system, such as repairing heart tissue after myocardial infarction, enhancing cardiomyocyte proliferation, improving cardiac regeneration after myocardial injury, regulating proliferation and survival of endothelial cells, reducing endothelial cell damage, resisting pressure overload-induced heart failure, as well as protecting against atherosclerosis. Furthermore, regarding the metabolic diseases, MYDGF has effects of improving type 2 diabetes mellitus, relieving non-alcoholic fatty liver disease, alleviating glomerular diseases, and resisting osteoporosis. Herein, we will discuss the biology of MYDGF and its effects on cardiovascular and metabolic diseases.

Key genes involved in nonalcoholic steatohepatitis improvement after bariatric surgery

Background

Nonalcoholic steatohepatitis (NASH) is the advanced stage of nonalcoholic fatty liver disease (NAFLD), one of the most prevalent chronic liver diseases. The effectiveness of bariatric surgery in treating NASH and preventing or even reversing liver fibrosis has been demonstrated in numerous clinical studies, but the underlying mechanisms and crucial variables remain unknown.

Methods

Using the GSE135251 dataset, we examined the gene expression levels of NASH and healthy livers. Then, the differentially expressed genes (DEGs) of patients with NASH, at baseline and one year after bariatric surgery, were identified in GSE83452. We overlapped the hub genes performed by protein-protein interaction (PPI) networks and DEGs with different expression trends in both datasets to obtain key genes. Genomic enrichment analysis (GSEA) and genomic variation analysis (GSVA) were performed to search for signaling pathways of key genes. Meanwhile, key molecules that regulate the key genes are found through the construction of the ceRNA network. NASH mice were induced by a high-fat diet (HFD) and underwent sleeve gastrectomy (SG). We then cross-linked the DEGs in clinical and animal samples using quantitative polymerase chain reaction (qPCR) and validated the key genes.

Results

Seven key genes (FASN, SCD, CD68, HMGCS1, SQLE, CXCL10, IGF1) with different expression trends in GSE135251 and GSE83452 were obtained with the top 30 hub genes selected by PPI. The expression of seven key genes in mice after SG was validated by qPCR. Combined with the qPCR results from NASH mice, the four genes FASN, SCD, HMGCS1, and CXCL10 are consistent with the biological analysis. The GSEA results showed that the 'cholesterol homeostasis' pathway was enriched in the FASN, SCD, HMGCS1, and SQLE high-expression groups. The high-expression groups of CD68 and CXCL10 were extremely enriched in inflammation-related pathways. The construction of the ceRNA network obtained microRNAs and ceRNAs that can regulate seven key genes expression.

Conclusion

In summary, this study contributes to our understanding of the mechanisms by which bariatric surgery improves NASH, and to the development of potential biomarkers for the treatment of NASH.

Identification of myeloid-derived growth factor as a mechanically-induced, growth-promoting angiocrine signal for human hepatocytes

Recently, we have shown that after partial hepatectomy (PHx), an increased hepatic blood flow initiates liver growth in mice by vasodilation and mechanically-triggered release of angiocrine signals. Here, we use mass spectrometry to identify a mechanically-induced angiocrine signal in human hepatic endothelial cells, that is, myeloid-derived growth factor (MYDGF). We show that it induces proliferation and promotes survival of primary human hepatocytes derived from different donors in two-dimensional cell culture, via activation of mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 3 (STAT3). MYDGF also enhances proliferation of human hepatocytes in three-dimensional organoids. In vivo, genetic deletion of MYDGF decreases hepatocyte proliferation in the regenerating mouse liver after PHx; conversely, adeno-associated viral delivery of MYDGF increases hepatocyte proliferation and MAPK signaling after PHx. We conclude that MYDGF represents a mechanically-induced angiocrine signal and that it triggers growth of, and provides protection to, primary mouse and human hepatocytes.

Genetic deletion of MMP12 ameliorates cardiometabolic disease by improving insulin sensitivity, systemic inflammation, and atherosclerotic features in mice

BACKGROUND

Matrix metalloproteinase 12 (MMP12) is a macrophage-secreted protein that is massively upregulated as a pro-inflammatory factor in metabolic and vascular tissues of mice and humans suffering from cardiometabolic diseases (CMDs). However, the molecular mechanisms explaining the contributions of MMP12 to CMDs are still unclear.

METHODS

We investigated the impact of MMP12 deficiency on CMDs in a mouse model that mimics human disease by simultaneously developing adipose tissue inflammation, insulin resistance, and atherosclerosis. To this end, we generated and characterized low-density lipoprotein receptor (Ldlr)/Mmp12-double knockout (DKO) mice fed a high-fat sucrose- and cholesterol-enriched diet for 16-20 weeks.

RESULTS

DKO mice showed lower cholesterol and plasma glucose concentrations and improved insulin sensitivity compared with LdlrKO mice. Untargeted proteomic analyses of epididymal white adipose tissue revealed that inflammation- and fibrosis-related pathways were downregulated in DKO mice. In addition, genetic deletion of MMP12 led to alterations in immune cell composition and a reduction in plasma monocyte chemoattractant protein-1 in peripheral blood which indicated decreased low-grade systemic inflammation. Aortic en face analyses and staining of aortic valve sections demonstrated reduced atherosclerotic plaque size and collagen content, which was paralleled by an improved relaxation pattern and endothelial function of the aortic rings and more elastic aortic sections in DKO compared to LdlrKO mice. Shotgun proteomics revealed upregulation of anti-inflammatory and atheroprotective markers in the aortas of DKO mice, further supporting our data. In humans, MMP12 serum concentrations were only weakly associated with clinical and laboratory indicators of CMDs.

CONCLUSION

We conclude that the genetic deletion of MMP12 ameliorates obesity-induced low-grade inflammation, white adipose tissue dysfunction, biomechanical properties of the aorta, and the development of atherosclerosis. Therefore, therapeutic strategies targeting MMP12 may represent a promising approach to combat CMDs.

Sweroside attenuates podocyte injury and proteinuria in part by activating Akt/BAD signaling in mice

In this study, we investigated the effects of sweroside on podocyte injury in diabetic nephropathy (DN) mice and elucidated its molecular mechanisms. We conducted in vivo experiments using a C57BL/6 mice model of DN to explore the effects of sweroside on proteinuria and podocyte injury in DN mice. In in vitro experiments, conditionally immortalized mouse podocytes were treated with high glucose and sweroside, and the protective effects of sweroside on podocyte injury were analyzed. In vitro, Akt/BAD pathways were detected using gene siRNA silencing assays and found to be involved in the protective roles of sweroside in high glucose-mediated podocyte injury. In vivo, sweroside significantly decreased albuminuria in DN mice (p < 0.01). periodic acid-Schiff staining showed that sweroside alleviated the glomerular volume and mesangium expansion in DN mice. Consistently, western blot and reverse transcription-polymerase chain reaction analyses showed that the profibrotic molecule expression in the glomeruli declined in sweroside-treated DN mice. Immunofluorescent results showed that sweroside preserved nephrin and podocin expression, and transmission electron microscopy showed that sweroside attenuated podocyte injury. In DN mice, sweroside decreased podocyte apoptosis, and increased nephrin, podocin expression and decreased desmin and HIF1α expression. These results confirmed that sweroside ameliorated albuminuria, glomerulomegaly, and glomerulosclerosis in these mice. Experiments in vitro revealed that sweroside improved HG-induced podocyte injury and apoptosis. Sweroside stimulated activation of the Akt/BAD pathway and upregulated Bcl-2-associated death promoter (BAD) and p-Akt. Overall, sweroside protected podocytes from injury and prevented the progression of DN, providing a novel strategy for the treatment of DN.