Oncostatin M Mediates Adipocyte Expression and Secretion of Stromal-Derived Factor 1

Adipocyte-Specific Laminin Alpha 4 Deletion Preserves Adipose Tissue Health despite Increasing Adiposity

Laminins are heterotrimeric glycoproteins with structural and functional roles in basement membranes. The predominant laminin alpha chain found in adipocyte basement membranes is laminin α4 (LAMA4). Global LAMA4 deletion in mice leads to reduced adiposity and increased energy expenditure, but also results in vascular defects that complicate the interpretation of metabolic data. Here, we describe the generation and initial phenotypic analysis of an adipocyte-specific LAMA4 knockout mouse (Lama4^AKO). We first performed an in-silico analysis to determine the degree to which laminin α4 was expressed in human and murine adipocytes. Next, male Lama4^AKO and control mice were fed chow or high-fat diets and glucose tolerance was assessed along with serum insulin and leptin levels. Adipocyte area was measured in both epididymal and inguinal white adipose tissue (eWAT and iWAT, respectively), and eWAT was used for RNA-sequencing. We found that laminin α4 was highly expressed in human and murine adipocytes. Further, chow-fed Lama4^AKO mice are like control mice in terms of body weight, body composition, and glucose tolerance, although they have larger eWAT adipocytes and lower insulin levels. High-fat-fed Lama4^AKO mice are fatter and more glucose tolerant when compared to control mice. Transcriptionally, the eWAT of high-fat fed Lama4^AKO mice resembles that of chow-fed control mice. We conclude from these findings that adipocyte-specific LAMA4 deletion is protective in an obesogenic environment, even though overall adiposity is increased.

Oncostatin M Induces Lipolysis and Suppresses Insulin Response in 3T3-L1 Adipocytes

Oncostatin M (OSM) is an immune cell-derived cytokine that is upregulated in adipose tissue in obesity. Upon binding its receptor (OSMR), OSM induces the phosphorylation of the p66 subunit of Src homology 2 domain-containing transforming protein 1 (SHC1), called p66Shc, and activates the extracellular signal-related kinase (ERK) pathway. Mice with adipocyte-specific OSMR deletion (Osmr^FKO) are insulin resistant and exhibit adipose tissue inflammation, suggesting that intact adipocyte OSM–OSMR signaling is necessary for maintaining adipose tissue health. How OSM affects specific adipocyte functions is still unclear. Here, we examined the effects of OSM on adipocyte lipolysis. We treated 3T3-L1 adipocytes with OSM, insulin, and/or inhibitors of SHC1 and ERK and measured glycerol release. We also measured phosphorylation of p66Shc, ERK, and insulin receptor substrate-1 (IRS1) and the expression of lipolysis-associated genes in OSM-exposed 3T3-L1 adipocytes and primary adipocytes from control and Osmr^FKO mice. We found that OSM induces adipocyte lipolysis via a p66Shc-ERK pathway and inhibits the suppression of lipolysis by insulin. Further, OSM induces phosphorylation of inhibitory IRS1 residues. We conclude that OSM is a stimulator of lipolysis and inhibits adipocyte insulin response. Future studies will determine how these roles of OSM affect adipose tissue function in health and disease.

Exploring the oncostatin M (OSM) feed-forward signaling of glioblastoma via STAT3 in pan-cancer analysis

Background

Oncostatin M (OSM) has been reported to be a key regulating factor in the process of tumor development. Previous studies have demonstrated both the promotion and inhibition effects of OSM in tumors, therefore inspiring controversies. However, no systematic assessment of OSM across various cancers is available, and the mechanisms behind OSM-related cancer progression remain to be elucidated.

Methods

Based on The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases, we conducted a pan-cancer analysis on OSM to explore its tumor-related functions across cancers as well as its correlations with specific molecules, cells in the tumor microenvironment. Considering the results of pan-cancer analysis, we chose the specific tumor glioblastoma multiforme (GBM) to screen out the OSM-induced signaling pathways and intercellular communications in tumor progression. Wound scratch assay, invasion assay and qRT-PCR were performed to verify the biological effects of OSM on glioblastoma cells.

Results

Higher OSM level was found in most tumor tissues compared with corresponding normal tissues, and the enhanced OSM expression was observed to be strongly related to patients’ poor prognosis in several cancers. Moreover, the expression of OSM was associated with stromal and immune cell infiltration in the tumor microenvironment, and OSM-related immune checkpoint and chemokine co-expression were also observed. Our results suggested that OSM could communicate extensively with the tumor microenvironment. Taking GBM as an example, our study found that two critical signaling pathways in OSM-related tumor progression by KEGG enrichment analysis: Jak-STAT and NF-κB pathways. Single-cell RNA sequencing data analysis of GBM revealed that OSM was mainly secreted by microglia, and cell–cell interaction analysis proved that OSM-OSMR is an important pathway for OSM to stimulate malignant cells. In vitro, OSM treatment could facilitate the migration and invasion of glioblastoma cells, meanwhile promote the proneural-mesenchymal transition. The administration of STAT3 inhibitors effectively suppressed the OSM-mediated biological effects, which proved the key role of STAT3 in OSM signaling.

Conclusion

Taken together, our study provides a comprehensive understanding with regard to the tumor progression under the regulation of OSM. OSM seems to be closely related to chronic inflammation and tumor development in the tumor microenvironment. As an important inflammatory factor in the tumor microenvironment, OSM may serve as a potential immunotherapeutic target for cancer treatment, especially for GBM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02260-9.

Role of Inflammatory Cytokines, Growth Factors and Adipokines in Adipogenesis and Insulin Resistance

Obesity, manifested by increased adiposity, represents a main cause of morbidity in the developed countries, causing increased risk of insulin resistance and type 2 diabetes mellitus. Recruitment of macrophages and activation of innate immunity represent the initial insult, which can be further exacerbated through secretion of chemokines and adipocytokines from activated macrophages and other cells within the adipose tissue. These events can impact adipogenesis, causing dysfunction of the adipose tissue and increased risk of insulin resistance. Various factors mediate adiposity and related insulin resistance including inflammatory and non-inflammatory factors such as pro and anti-inflammatory cytokines, adipokines and growth factors. In this review we will discuss the role of these factors in adipogenesis and development of insulin resistance and type 2 diabetes mellitus in the context of obesity. Understanding the molecular mechanisms that mediate adipogenesis and insulin resistance could help the development of novel therapeutic strategies for individuals at higher risk of insulin resistance and type 2 diabetes mellitus.

Adipocyte Oncostatin Receptor Regulates Adipose Tissue Homeostasis and Inflammation

Adipocytes are the largest cell type in terms of volume, but not number, in adipose tissue. Adipocytes are prominent contributors to systemic metabolic health. Obesity, defined by excess adipose tissue (AT), is recognized as a low-grade chronic inflammatory state. Cytokines are inflammatory mediators that are produced in adipose tissue (AT) and function in both AT homeostatic as well as pathological conditions. AT inflammation is associated with systemic metabolic dysfunction and obesity-associated infiltration and proliferation of immune cells occurs in a variety of fat depots in mice and humans. AT immune cells secrete a variety of chemokines and cytokines that act in a paracrine manner on adjacent adipocytes. TNFα, IL-6, and MCP-1, are well studied mediators of AT inflammation. Oncostatin M (OSM) is another proinflammatory cytokine that is elevated in AT in human obesity, and its specific receptor (OSMRβ) is also induced in conditions of obesity and insulin resistance. OSM production and paracrine signaling in AT regulates adipogenesis and the functions of AT. This review summarizes the roles of the oncostatin M receptor (OSMRβ) as a modulator of adipocyte development and function its contributions to immunological adaptations in AT in metabolic disease states.