Stromelysin-1 regulates adipogenesis during mammary gland involution

Exploring the role of dermal sheath cells in wound healing and fibrosis

Wound healing is a complex, dynamic process involving the coordinated interaction of diverse cell types, growth factors, cytokines, and extracellular matrix components. Despite emerging evidence highlighting their importance, dermal sheath cells remain a largely overlooked aspect of wound healing research. This review explores the multifunctional roles of dermal sheath cells in various phases of wound healing, including modulating inflammation, aiding in proliferation, and contributing to extracellular matrix remodelling. Special attention is devoted to the paracrine effects of dermal sheath cells and their role in fibrosis, highlighting their potential in improving healing outcomes, especially in differentiating between hairy and non-hairy skin sites. By drawing connections between dermal sheath cells activity and wound healing outcomes, this work proposes new insights into the mechanisms of tissue regeneration and repair, marking a step forward in our understanding of wound healing processes.

Host response during unresolved urinary tract infection alters female mammary tissue homeostasis through collagen deposition and TIMP1

Exposure to pathogens throughout a lifetime influences immunity and organ function. Here, we explore how the systemic host-response to bacterial urinary tract infection (UTI) induces tissue-specific alterations to the mammary gland. Utilizing a combination of histological tissue analysis, single cell transcriptomics, and flow cytometry, we identify that mammary tissue from UTI-bearing mice displays collagen deposition, enlarged ductal structures, ductal hyperplasia with atypical epithelial transcriptomes and altered immune composition. Bacterial cells are absent in the mammary tissue and blood of UTI-bearing mice, therefore, alterations to the distal mammary tissue are mediated by the systemic host response to local infection. Furthermore, broad spectrum antibiotic treatment resolves the infection and restores mammary cellular and tissue homeostasis. Systemically, unresolved UTI correlates with increased plasma levels of the metalloproteinase inhibitor, TIMP1, which controls extracellular matrix remodeling and neutrophil function. Treatment of nulliparous and post-lactation UTI-bearing female mice with a TIMP1 neutralizing antibody, restores mammary tissue normal homeostasis, thus providing evidence for a link between the systemic host response during UTI and mammary gland alterations.

Adipocyte Precursor-Derived NRG1 Promotes Resistance to FGFR Inhibition in Urothelial Carcinoma

Aberrations of the fibroblast growth factor receptor (FGFR) family members are frequently observed in metastatic urothelial cancer (mUC), and blocking the FGF/FGFR signaling axis is used as a targeted therapeutic strategy for treating patients. Erdafitinib is a pan-FGFR inhibitor, which has recently been approved by the FDA for mUC with FGFR2/3 alterations. Although mUC patients show initial response to erdafitinib, acquired resistance rapidly develops. Here, we found that adipocyte precursors promoted resistance to erdafitinib in FGFR-dependent bladder and lung cancer in a paracrine manner. Moreover, neuregulin 1 (NRG1) secreted from adipocyte precursors was a mediator of erdafitinib resistance by activating human epidermal growth factor receptor 3 (ERBB3; also known as HER3) signaling, and knockdown of NRG1 in adipocyte precursors abrogated the conferred paracrine resistance. NRG1 expression was significantly downregulated in terminally differentiated adipocytes compared with their progenitors. Pharmacologic inhibition of the NRG1/HER3 axis using pertuzumab reversed erdafitinib resistance in tumor cells in vitro and prolonged survival of mice bearing bladder cancer xenografts in vivo. Remarkably, data from single-cell RNA sequencing revealed that NRG1 was enriched in platelet-derived growth factor receptor-A (PDGFRA) expressing inflammatory cancer-associated fibroblasts, which is also expressed on adipocyte precursors. Together, this work reveals a paracrine mechanism of anti-FGFR resistance in bladder cancer, and potentially other cancers, that is amenable to inhibition using available targeted therapies.

SIGNIFICANCE

Acquired resistance to FGFR inhibition can be rapidly promoted by paracrine activation of the NRG1/HER3 axis mediated by adipocyte precursors and can be overcome by the combination of pertuzumab and erdafitinib treatment. See related commentary by Kolonin and Anastassiou, p. 648.

Mature white adipocyte plasticity during mammary gland remodelling and cancer

Mammary gland growth and differentiation predominantly rely on stromal-epithelial cellular communication. Specifically, mammary adipocytes play a crucial role in ductal morphogenesis, as well as in the proliferation and differentiation of mammary epithelial cells. The process of lactation entails a reduction in the levels of white adipose tissue associated with the MG, allowing for the expansion of milk-producing epithelial cells. Subsequently, during involution and the regression of the milk-producing unit, adipocyte layers resurface, occupying the vacated space. This dynamic phenomenon underscores the remarkable plasticity and expansion of adipose tissue. Traditionally considered terminally differentiated, adipocytes have recently been found to exhibit plasticity in certain contexts. Unraveling the significance of this cell type within the MG could pave the way for novel approaches to reduce the risk of breast cancer and enhance lactation performance. Moreover, a comprehensive understanding of adipocyte trans- and de-differentiation processes holds promise for the development of innovative therapeutic interventions targeting cancer, fibrosis, obesity, type 2 diabetes, and other related diseases. Additionally, adipocytes may find utility in the realm of regenerative medicine. This review article provides a comprehensive examination of recent advancements in our understanding of MG remodelling, with a specific focus on the tissue-specific functions of adipocytes and their role in the development of cancer. By synthesizing current knowledge in this field, it aims to consolidate our understanding of adipocyte biology within the context of mammary gland biology, thereby fostering further research and discovery in this vital area.

Roles of Matrix Metalloproteinases and Their Natural Inhibitors in Metabolism: Insights into Health and Disease

Matrix metalloproteinases (MMPs) are a family of zinc-activated peptidases that can be classified into six major classes, including gelatinases, collagenases, stromelysins, matrilysins, membrane type metalloproteinases, and other unclassified MMPs. The activity of MMPs is regulated by natural inhibitors called tissue inhibitors of metalloproteinases (TIMPs). MMPs are involved in a wide range of biological processes, both in normal physiological conditions and pathological states. While some of these functions occur during development, others occur in postnatal life. Although the roles of several MMPs have been extensively studied in cancer and inflammation, their function in metabolism and metabolic diseases have only recently begun to be uncovered, particularly over the last two decades. This review aims to summarize the current knowledge regarding the metabolic roles of metalloproteinases in physiology, with a strong emphasis on adipose tissue homeostasis, and to highlight the consequences of impaired or exacerbated MMP actions in the development of metabolic disorders such as obesity, fatty liver disease, and type 2 diabetes.

Effect of a diet based on the dietary guidelines for americans on inflammation markers in women at risk for cardiometabolic disease: results of a randomized, controlled trial

OBJECTIVE

To evaluate the effect of a diet pattern based on Dietary Guidelines for Americans (DGA), in a controlled feeding setting, on plasma markers of inflammation and on cytokine production by peripheral blood mononuclear cells (PBMC).

DESIGN

Women (n = 44) with one or more risk factors of metabolic syndrome (and BMI: 25.2-39.8 kg/m2) completed an 8-wk controlled feeding study. They were randomized to either a group following a diet based on DGA 2010 (DGA), or a group given a 'typical American diet' (TAD), based largely on a Western diet pattern. By design, women maintained their body weight. Fasting plasma and PBMC were collected at wk. 0 (baseline) and at wk. 8 (post-intervention). Sixteen plasma markers of inflammation and eight PBMC cytokines were measured at both time points, to evaluate if the diet had a significant effect on concentrations of these inflammatory markers. Data were analyzed using ANCOVA, followed by multiple-comparison adjustment using Benjamini-Hochberg method.

RESULTS

Significant changes observed in Serum Amyloid A (SAA) and Matrix Metalloproteinase 3 (MMP3) in plasma did not retain significance upon multiple comparison adjustment. SAA: p = 0.044, adj p = 0.450; DGA mean change [95% CI] = - 12.6[- 32.3 to 7.04]; TAD mean change [95% CI] = - 2.24 [- 9.99 to 5.51]. MMP3: p = 0.014, adj p = 0.35; DGA mean change [95% CI] = 2.72[- 4.16 to 9.59]; TAD mean change [95% CI] = - 0.98[- 16.7 to 14.7]). Other inflammation markers were not differently altered by DGA relative to TAD. Effect size of change (Cohens d) indicated a large/medium-large effect of intervention on MMP3 and CRP, and medium effect on IL-6.

CONCLUSIONS

No statistically significant changes were observed in the immune markers examined in this study. The biological roles and magnitude of the non-significant differences seen with two variables, CRP and MMP3, suggest that they be examined in future studies.

TRIAL REGISTRATION

Clinicaltrials.gov identifier NCT02298725.

Adipocyte plasticity in tissue regeneration, repair, and disease

Mammalian tissue repair forms a scar that fills the injured area with a fibrotic lesion, limiting tissue function. Adipocytes, lipid-filled cells, well-known for energy storage and endocrine functions, can reside adjacent to or within many tissues, and are emerging as critical regulators of tissue repair. In this review, the plasticity and function of adipocytes to tissue repair and fibrosis in four tissues: skin, heart, skeletal muscle, and mammary gland, will be discussed. The dynamic nature of adipocytes as they release bioactive products, lipids, and adipokines, and their ability to form contractile fibroblasts, is emerging as an essential regulator of wound healing and tumorigenesis in multiple tissues. Thus, modulation of adipocytes may provide therapeutic avenues for regenerative medicine and cancer.

MMPs and TIMPs levels are correlated with anthropometric parameters, blood pressure, and endothelial function in obesity

The association between matrix metalloproteinases (MMPs), tissue inhibitor of metalloproteinases (TIMPs) and obesity as well as obesity-related disease including metabolic syndrome is not fully explored. Our aims are that: (i) to evaluate the plasma levels of MMP-1, MMP-2, MMP-3, MMP-9, TIMP-1, TIMP-2 and their ratios in non-obese people, overweight and obese people with or without metabolic syndrome, (ii) to investigate correlations between MMPs or TIMPs levels and several anthropometric parameters, blood pressure, endothelial function. Anthropometric and biochemical parameters were determined in 479 randomly selected participants, subdividing according to body mass index (BMI) and metabolic syndrome status. Plasma MMPs and TIMPs levels were measured. The assessment of endothelial function was characterized in people with obesity, overweight and non-obese, using laser Doppler Flowmetry. Obese people have elevated MMP-1, MMP-2, TIMP-1, TIMP-2 levels and decreased MMP-3/TIMP-1 and MMP-9/TIMP-1 ratios compared with non-obese people. MMP-1 levels and MMP-1/TIMP-1 ratio were positively correlated with BMI and waist circumference (WC) while MMP-2 levels were negatively correlated with BMI and WC values in obese people. MMP-3 levels and MMP-3/TIMP-1 ratio were positively correlated with systolic blood pressure (SBP) or diastolic blood pressure (DBP) in obese and metabolic syndrome people. Additionally, MMP-9 levels and MMP-9/TIMP-1 ratio were negatively correlated with endothelium-dependent response in obese and metabolic syndrome people. MMP-1, MMP-2, TIMP-1, TIMP-2 levels were increased in obese subjects. Significant correlations between anthropometric parameters and MMP-1 as well as MMP-1/TIMP-1 ratio supported these results. MMP-3 and -9 levels as well as their ratios with TIMP-1 were associated with blood pressure and endothelial-dependent response, respectively. In conclusion, our results demonstrated that MMP-1, MMP-3 and MMP-9 levels were correlated with several obesity-related parameters including BMI, WC, blood pressure and endothelial-dependent response. Our findings will hopefully provide new aspects for the use of MMPs and TIMPs as clinical biomarkers in obesity-related cardiovascular diseases such as metabolic syndrome and hypertension. The lack of measure of MMPs activity in plasma and relevant organs/tissues in obesity and metabolic syndrome is considered as a limitation in this report.

Metalloproteinases 1 and 3 as Potential Biomarkers in Breast Cancer Development

Breast cancer continues to be one of the main causes of morbidity and mortality globally and was the leading cause of cancer death in women in Spain in 2020. Early diagnosis is one of the most effective methods to lower the incidence and mortality rates of breast cancer. The human metalloproteinases (MMP) mainly function as proteolytic enzymes degrading the extracellular matrix and plays important roles in most steps of breast tumorigenesis. This retrospective cohort study shows the immunohistochemical expression levels of MMP-1, MMP-2, MMP-3, and MMP-9 in 154 women with breast cancer and 42 women without tumor disease. The samples of breast tissue are assessed using several tissue matrices (TMA). The percentages of staining (≤50%–>50%) and intensity levels of staining (weak, moderate, or intense) are considered. The immunohistochemical expression of the MMP-1-intensity (p = 0.043) and MMP-3 percentage (p = 0.018) and intensity, (p = 0.025) present statistically significant associations with the variable group (control–case); therefore, expression in the tumor tissue samples of these MMPs may be related to the development of breast cancer. The relationships between these MMPs and some clinicopathological factors in breast cancer are also evaluated but no correlation is found. These results suggest the use of MMP-1 and MMP-3 as potential biomarkers of breast cancer diagnosis.

Extracellular Matrix-Related Hubs Genes Have Adverse Effects on Gastric Adenocarcinoma Prognosis Based on Bioinformatics Analysis

Gastric adenocarcinoma (GAC) is the most frequent type of stomach cancer, characterized by high heterogeneity and phenotypic diversity. Although many novel strategies have been developed for treating GAC, recurrence and metastasis rates are still high. Therefore, it is necessary to screen new potential biomarkers correlated with prognosis and novel molecular targets. Gene expression profiles were obtained from the from NCBI Gene Expression Omnibus (GEO) database. We conduct an integrated analysis using the online Venny website to explore candidate hub genes between differentially expressed genes (DEGs) of two datasets. Gene ontology (GO) and Kyoto Encyclopedia 18 of Genes and Genomes (KEGG) pathway enrichment analysis found that extracellular matrix plays an important role in GAC. In addition, we applied protein-protein interaction (PPI) network analysis by using the Search Tool for the Retrieval of Interacting Genes (STRING) and visualized with Cytoscape software. Furthermore, we employed Cytoscape software to analyze the interactive relationship of candidate gene for further analysis. We found that ECM related proteins played an important role in GAC, and 15 hub genes were extracted from 123 DEGs genes. There were four hub genes (bgn, vcan, col1a1 and timp1) predicted to be associated with poor prognosis among the 15 hub genes.

Matrix Metalloproteinase 3: A Promoting and Destabilizing Factor in the Pathogenesis of Disease and Cell Differentiation

Cells must alter their expression profiles and morphological characteristics but also reshape the extracellular matrix (ECM) to fulfill their functions throughout their lifespan. Matrix metalloproteinase 3 (MMP-3) is a member of the matrix metalloproteinase (MMP) family, which can degrade multiple ECM components. MMP-3 can activate multiple pro-MMPs and thus initiates the MMP-mediated degradation reactions. In this review, we summarized the function of MMP-3 and discussed its effects on biological activities. From this point of view, we emphasized the positive and negative roles of MMP-3 in the pathogenesis of disease and cell differentiation, highlighting that MMP-3 is especially closely involved in the occurrence and development of osteoarthritis. Then, we discussed some pathways that were shown to regulate MMP-3. By writing this review, we hope to provide new topics of interest for researchers and attract more researchers to investigate MMP-3.

The Roles of Matrix Metalloproteinases and Their Inhibitors in Human Diseases

Matrix metalloproteinases (MMPs) are a family of zinc-dependent extracellular matrix (ECM) remodeling endopeptidases that have the capacity to degrade almost every component of the ECM. The degradation of the ECM is of great importance, since it is related to embryonic development and angiogenesis. It is also involved in cell repair and the remodeling of tissues. When the expression of MMPs is altered, it can generate the abnormal degradation of the ECM. This is the initial cause of the development of chronic degenerative diseases and vascular complications generated by diabetes. In addition, this process has an association with neurodegeneration and cancer progression. Within the ECM, the tissue inhibitors of MMPs (TIMPs) inhibit the proteolytic activity of MMPs. TIMPs are important regulators of ECM turnover, tissue remodeling, and cellular behavior. Therefore, TIMPs (similar to MMPs) modulate angiogenesis, cell proliferation, and apoptosis. An interruption in the balance between MMPs and TIMPs has been implicated in the pathophysiology and progression of several diseases. This review focuses on the participation of both MMPs (e.g., MMP-2 and MMP-9) and TIMPs (e.g., TIMP-1 and TIMP-3) in physiological processes and on how their abnormal regulation is associated with human diseases. The inclusion of current strategies and mechanisms of MMP inhibition in the development of new therapies targeting MMPs was also considered.

Regulation of the JAK2-STAT5 Pathway by Signaling Molecules in the Mammary Gland

Janus kinase 2 (JAK2) and signal transducers and activators of transcription 5 (STAT5) are involved in the proliferation, differentiation, and survival of mammary gland epithelial cells. Dysregulation of JAK2-STAT5 activity invariably leads to mammary gland developmental defects and/or diseases, including breast cancer. Proper functioning of the JAK2-STAT5 signaling pathway relies on crosstalk with other signaling pathways (synergistically or antagonistically), which leads to normal biological performance. This review highlights recent progress regarding the critical components of the JAK2-STAT5 pathway and its crosstalk with G-protein coupled receptor (GPCR) signaling, PI3K-Akt signaling, growth factors, inflammatory cytokines, hormone receptors, and cell adhesion.

Tissue Inhibitor of Metalloprotease-1 (TIMP-1) Regulates Adipogenesis of Adipose-derived Stem Cells (ASCs) via the Wnt Signaling Pathway in an MMP-independent Manner

Tissue inhibitor of metalloprotease-1 (TIMP-1) is a tissue inhibitor of matrix metalloproteinases (MMPs). It however exerts multiple effects on biological processes, such as cell growth, proliferation, differentiation and apoptosis, in an MMP-independent manner. This study aimed to examine the role of TIMP-1 in adipogenesis of adipose-derived stem cells (ASCs) and the underlying mechanism. We knocked down the TIMP-1 gene in ASCs through lentiviral vectors encoding TIMP-1 small interfering RNA (siRNA), and then found that the knockdown of TIMP-1 in ASCs promoted the adipogenic differentiation of stem cells and inhibited the Wnt/β-catenin signaling pathway in ASCs. We also noted that mutant TIMP-1 without the inhibitory activity on MMPs promoted the activation of Wnt/β-catenin pathway as well as the recombinant wild type TIMP-1 did, which indicated that the effect of TIMP-1 on Wnt/β-catenin pathway was MMP-independent. Our study suggested that TIMP-1 negatively regulated the adipogenesis of ASCs via the Wnt/β-catenin signaling pathway in an MMP-independent manner.

Tm7sf2 gene promotes adipocyte differentiation of mouse embryonic fibroblasts and improves insulin sensitivity

Adipogenesis is a finely orchestrated program involving a transcriptional cascade coordinated by CEBP and PPAR family members and by hormonally induced signaling pathways. Alterations in any of these factors result into impaired formation of fully differentiated adipocytes. Tm7sf2 gene encodes for a Δ(14)-sterol reductase primarily involved in cholesterol biosynthesis. Furthermore, TM7SF2 modulates the expression of the master gene of adipogenesis PPARγ, suggesting a role in the regulation of adipose tissue homeostasis. We investigated the differentiation of Tm7sf2^-/- MEFs into adipocytes, compared to Tm7sf2^+/+ MEFs. Tm7sf2 expression was increased at late stage of differentiation in wild type cells, while Tm7sf2^-/- MEFs exhibited a reduced capacity to differentiate into mature adipocytes. Indeed, Tm7sf2^-/- MEFs had lower neutral lipid accumulation and reduced expression of adipogenic regulators. At early stage, the reduction in C/EBPβ expression impaired mitotic clonal expansion, which is needed by preadipocytes for adipogenesis induction. At late stage, the expression and activity of C/EBPα and PPARγ were inhibited in Tm7sf2^-/- cells, leading to the reduced expression of adipocyte genes like Srebp-1c, Fasn, Scd-1, Adipoq, Fabp4, and Glut4. Loss of the acquisition of adipocyte phenotype was accompanied by a reduction in the levels of Irs1, and phosphorylated Akt and ERK1/2, indicating a blunted insulin signaling in differentiating Tm7sf2^-/- cells. Moreover, throughout the differentiation process, increased expression of the antiadipogenic Mmp3 was observed in MEFs lacking Tm7sf2. These findings indicate Tm7sf2 as a novel factor influencing adipocyte differentiation that could be relevant to adipose tissue development and maintenance of metabolic health.

Stromal metalloproteinases: Crucial contributors to the tumor microenvironment

Proteolytic balance is crucial for the maintenance of tissue homeostasis. In cancer, dysregulated proteolysis is involved in unregulated tissue remodeling and inflammation, leading to the promotion of tumor growth, local invasion, and metastasis. Metalloproteinases, which were first identified as collagen cleaving enzymes, have been shown to extensively degrade extracellular matrix proteins or selectively release cell surface-bound cytokines, growth factors, or their receptors, thereby impacting extracellular matrix integrity, immune cell recruitment and tissue turnover. Although tumor cells produce various metalloproteinases, the major source is thought to be stromal cells infiltrating the tumor. Different types of stromal cells express specific sets of metalloproteinases and their inhibitors, which specifically alter the milieu within the tumor. In this review, recent findings and knowledge regarding metalloproteinases derived from stromal cells during the creation of the tumor microenvironment are described and their contribution to the tumor progression and metastasis discussed.

The Importance of Breast Adipose Tissue in Breast Cancer

Adipose tissue is a complex endocrine organ, with a role in obesity and cancer. Adipose tissue is generally linked to excessive body fat, and it is well known that the female breast is rich in adipose tissue. Hence, one can wonder: what is the role of adipose tissue in the breast and why is it required? Adipose tissue as an organ consists of adipocytes, an extracellular matrix (ECM) and immune cells, with a significant role in the dynamics of breast changes throughout the life span of a female breast from puberty, pregnancy, lactation and involution. In this review, we will discuss the importance of breast adipose tissue in breast development and its involvement in breast changes happening during pregnancy, lactation and involution. We will focus on understanding the biology of breast adipose tissue, with an overview on its involvement in the various steps of breast cancer development and progression. The interaction between the breast adipose tissue surrounding cancer cells and vice-versa modifies the tumor microenvironment in favor of cancer. Understanding this mutual interaction and the role of breast adipose tissue in the tumor microenvironment could potentially raise the possibility of overcoming breast adipose tissue mediated resistance to therapies and finding novel candidates to target breast cancer.

Estrogen exacerbates mammary involution through neutrophil-dependent and -independent mechanism

There is strong evidence that the pro-inflammatory microenvironment during post-partum mammary involution promotes parity-associated breast cancer. Estrogen exposure during mammary involution drives tumor growth through neutrophils’ activity. However, how estrogen and neutrophils influence mammary involution are unknown. Combined analysis of transcriptomic, protein, and immunohistochemical data in BALB/c mice showed that estrogen promotes involution by exacerbating inflammation, cell death and adipocytes repopulation. Remarkably, 88% of estrogen-regulated genes in mammary tissue were mediated through neutrophils, which were recruited through estrogen-induced CXCR2 signalling in an autocrine fashion. While neutrophils mediate estrogen-induced inflammation and adipocytes repopulation, estrogen-induced mammary cell death was via lysosome-mediated programmed cell death through upregulation of cathepsin B, Tnf and Bid in a neutrophil-independent manner. Notably, these multifaceted effects of estrogen are mostly mediated by ERα and unique to the phase of mammary involution. These findings are important for the development of intervention strategies for parity-associated breast cancer.

Tissue inhibitor matrix metalloproteinase 1 and risk of type 2 diabetes in a Chinese population

INTRODUCTION

The non-invasive enhanced liver fibrosis (ELF) score-comprising tissue inhibitor of matrix metalloproteinases-1 (TIMP1), hyaluronic acid (HA) and amino-terminal propeptide of type III procollagen (PIIINP)-has been shown to accurately predict fibrosis stages among patients with non-alcoholic fatty liver disease (NAFLD). However, no study has examined whether the ELF score or its components would also be predictive of type 2 diabetes, which commonly coexists and shares the same pathogenic abnormalities with NAFLD. Therefore, we prospectively investigated their associations with type 2 diabetes risks for the first time.

RESEARCH DESIGN AND METHODS

The ELF score was measured among 254 type 2 diabetes cases and 254 age-matched and sex-matched controls nested within the prospective Singapore Chinese Health Study. Cases had hemoglobin A1c (HbA1c) levels <6.5% at blood collection (1999-2004) and reported to have diabetes during follow-up II (2006-2010). Controls had HbA1c levels <6.0% at blood-taking and remained free of diabetes at follow-up II. Multivariable conditional logistic regression models were used to assess the ELF-diabetes association.

RESULTS

Higher TIMP1 levels were associated with increased type 2 diabetes risk, and the OR comparing the highest versus lowest quartiles was 2.56 (95% CI 1.23 to 5.34; p trend=0.035). However, ELF score, PIIINP and HA were not significantly associated with type 2 diabetes risks.

CONCLUSIONS

Higher TIMP1 levels, but not ELF score, PIIIMP and HA, were associated with increased type 2 diabetes risk in Chinese adults. Our results suggested that elevated TIMP1 levels may contribute to the type 2 diabetes development through pathways other than liver fibrosis.

Brucella abortus Infection Modulates 3T3-L1 Adipocyte Inflammatory Response and Inhibits Adipogenesis

Brucellosis is a prevalent global zoonotic infection but has far more impact in developing countries. The adipocytes are the most abundant cell type of adipose tissue and their secreted factors play an important role in several aspects of the innate and adaptive immune response. Here, we demonstrated the ability of Brucella abortus to infect and replicate in both adipocytes and its precursor cells (pre-adipocytes) derived from 3T3-L1 cell line. Additionally, infection of pre-adipocytes also inhibited adipogenesis in a mechanism independent of bacterial viability and dependent on lipidated outer membrane protein (L-Omp19). B. abortus infection was able to modulate the secretion of IL-6 and the matrix metalloproteases (MMPs) -2 and-9 in pre-adipocytes and adipocytes, and also modulated de transcription of adiponectin, leptin, and resistin in differentiated adipocytes. B. abortus-infected macrophages also modulate adipocyte differentiation involving a TNF-α dependent mechanism, thus suggesting a plausible interplay between B. abortus, adipocytes, and macrophages. In conclusion, B. abortus is able to alter adipogenesis process in adipocytes and its precursors directly after their infection, or merely their exposure to the B. abortus lipoproteins, and indirectly through soluble factors released by B. abortus-infected macrophages.

Dynamic architectural interplay between leucocytes and mammary epithelial cells

The adult mammary gland undergoes dynamic changes during puberty and the postnatal developmental cycle. The mammary epithelium is composed of a bilayer of outer basal, or myoepithelial, cells and inner luminal cells, the latter lineage giving rise to the milk-producing alveolar cells during pregnancy. These luminal alveolar cells undergo Stat3-mediated programmed cell death following the cessation of lactation. It is established that immune cells in the microenvironment of the gland have a role to play both in the ductal outgrowth during puberty and in the removal of dead cells and remodelling of the stroma during the process of postlactational regression. However, most studies have focussed on the role of the stromal immune cell compartment or have quantified immune cell populations in tissue extracts. Our recent development of protocols for deep imaging of the mammary gland in three dimensions (3D) has enabled the architectural relationship between immune cells and the epithelium to be examined in detail, and we have discovered a surprisingly dynamic relationship between the basal epithelium and leucocytes. Furthermore, we have observed morphological changes in the myoepithelial cells, as involution progresses, which were not revealed by previous work in 2D tissue sections and whole tissue. This dynamic architecture suggests a role for myoepithelial cells in the orderly progression of involution. We conclude that deep imaging of mammary gland and other tissues is essential for analysing complex interactions between cellular compartments.

Fat fibrosis: friend or foe?

At the simplest level, obesity is the manifestation of an imbalance between caloric intake and expenditure; however, the pathophysiological mechanisms that govern the development of obesity and associated complications are enormously complex. Fibrosis within the adipose tissue compartment is one such factor that may influence the development of obesity and/or obesity-related comorbidities. Furthermore, the functional consequences of adipose tissue fibrosis are a matter of considerable debate, with evidence that fibrosis serves both adaptive and maladaptive roles. Tissue fibrosis itself is incompletely understood, and multiple cellular and molecular pathways are involved in the development, maintenance, and resolution of the fibrotic state. Within the context of obesity, fibrosis influences molecular and cellular events that relate to adipocytes, inflammatory cells, inflammatory mediators, and supporting adipose stromal tissue. In this Review, we explore what is known about the interplay between the development of adipose tissue fibrosis and obesity, with a view toward future investigative and therapeutic avenues.

Adipocyte hypertrophy and lipid dynamics underlie mammary gland remodeling after lactation

Adipocytes undergo pronounced changes in size and behavior to support diverse tissue functions, but the mechanisms that control these changes are not well understood. Mammary gland-associated white adipose tissue (mgWAT) regresses in support of milk fat production during lactation and expands during the subsequent involution of milk-producing epithelial cells, providing one of the most marked physiological examples of adipose growth. We examined cellular mechanisms and functional implications of adipocyte and lipid dynamics in the mouse mammary gland (MG). Using in vivo analysis of adipocyte precursors and genetic tracing of mature adipocytes, we find mature adipocyte hypertrophy to be a primary mechanism of mgWAT expansion during involution. Lipid tracking and lipidomics demonstrate that adipocytes fill with epithelial-derived milk lipid. Furthermore, ablation of mgWAT during involution reveals an essential role for adipocytes in milk trafficking from, and proper restructuring of, the mammary epithelium. This work advances our understanding of MG remodeling and tissue-specific roles for adipocytes.

FSP1-positive fibroblasts are adipogenic niche and regulate adipose homeostasis

Adipocyte progenitors reside in the stromal vascular fraction (SVF) of adipose tissues that are composed of fibroblasts, immune cells, and endothelial cells. It remains to be elucidated how the SVF regulates adipocyte progenitor fate determination and adipose homeostasis. Here, we report that fibroblast-specific protein-1 (FSP1)⁺ fibroblasts in the SVF are essential to adipose homeostasis. FSP1⁺ fibroblasts, devoid of adipogenic potential, are adjacent to the preadipocytes in the SVF. Ablation of FSP1⁺ fibroblasts in mice severely diminishes fat content of adipose depots. Activation of canonical Wnt signaling in the FSP1⁺ fibroblasts results in gradual loss of adipose tissues and resistance to diet-induced obesity. Alterations in the FSP1⁺ fibroblasts reduce platelet-derived growth factor (PDGF)-BB signaling and result in the loss of preadipocytes. Reduced PDGF-BB signaling, meanwhile, impairs the adipogenic differentiation capability of preadipocytes by regulating matrix metalloproteinase (MMP) expression, extracellular matrix remodeling, and the activation of Yes-associated protein (YAP) signaling. Thus, FSP1⁺ fibroblasts are an important niche essential to the maintenance of the preadipocyte pool and its adipogenic potential in adipose homeostasis.

White adipose tissue (WAT), which consists mostly of adipocytes, is not only a passive energy storage but also an active metabolic and endocrine organ in the body. The importance of maintaining proper adipose mass is emphasized by the fact that both adipose tissue excess—in obese individuals—and deficiency have adverse metabolic consequences. In order to maintain the number of adipocytes, there is a continuous turnover from preadipocytes in adults. Like any other adult stem cells and progenitor cells, cell fate and differentiation capability of preadipocytes are tightly regulated by a highly specialized niche. However, what constitutes the preadipocyte niche, and how the niche regulates preadipocyte function and adipose homeostasis, remain poorly known. In this study, we have identified fibroblast-specific protein-1 (FSP1)⁺ fibroblasts in the WAT stromal vascular fraction (SVF) of mice as the niche for preadipocytes. We show that FSP1⁺ fibroblasts with aberrant Wnt signaling fail to maintain the preadipocyte pool and its differentiation potential, resulting in loss of adipose tissue. We conclude that FSP1⁺ fibroblasts are a niche for preadipocytes and regulate adipose tissue homeostasis in adult mice.

Stromal cells in breast cancer as a potential therapeutic target

Breast cancer in the United States is the second most commonly diagnosed cancer in women. About 1 in 8 women will develop invasive breast cancer over the course of her lifetime and breast cancer remains the second leading cause of cancer-related death. In pursuit of novel therapeutic strategies, researchers have examined the tumor microenvironment as a potential anti-cancer target. In addition to neoplastic cells, the tumor microenvironment is composed of several critical normal cell types, including fibroblasts, vascular and lymph endothelial cells, osteoclasts, adipocytes, and immune cells. These cells have important roles in healthy tissue stasis, which frequently are altered in tumors. Indeed, tumor-associated stromal cells often contribute to tumorigenesis, tumor progression, and metastasis. Consequently, these host cells may serve as a possible target in anti-tumor and anti-metastatic therapeutic strategies. Targeting the tumor associated host cells offers the benefit that such cells do not mutate and develop resistance in response to treatment, a major cause of failure in cancer therapeutics targeting neoplastic cells. This review discusses the role of host cells in the tumor microenvironment during tumorigenesis, progression, and metastasis, and provides an overview of recent developments in targeting these cell populations to enhance cancer therapy efficacy.

Cancer Invasion: Watch Your Neighbourhood!

The critical event in neoplastic diseases is the invasion of surrounding tissue by cancer cells. This event greatly reduces treatment options, and makes cancer a lethal disease. Factors that initiate cancer invasion are not well understood, neither do we have mechanistic insights in the process itself. Recently, a new concept has emerged: the tissue surrounding tumor cells, ie, the tumor microenvironment, may play an important, if not decisive role in triggering invasion. This concept is based on data from many laboratories working on the cell biology of cancer invasion. In this review, we survey several components of the tumor microenvironment, including extracellular matrix macromolecules, metalloproteinases and soluble factors, and discuss their potential involvement in stimulating cancer cell motility. These novel views may have far-reaching consequences, since “normal” tissue microenvironment components, rather than the traditional tumor cells themselves, may eventually become targets for devising new treatments that prevent, inhibit or block cancer invasion and metastasis.

Extracellular matrix dynamics during mesenchymal stem cells differentiation

Mesenchymal stem cells (MSCs) are stromal cells that display self-renewal and multipotent differentiation capacity. The repertoire of mature cells generated ranges but is not restricted to: fat, bone and cartilage. Their potential importance for both cell therapy and maintenance of in vivo homeostasis is indisputable. Nonetheless, both their in vivo identity and use in cell therapy remain elusive. A drawback generated by this fact is that little is known about the MSC niche and how it impacts differentiation and homeostasis maintenance. Hence, the roles played by the extracellular matrix (ECM) and its main regulators namely: the Matrix Metalloproteinases (MMPs) and their counteracting inhibitors (TIMPs and RECK) upon stem cells differentiation are only now beginning to be unveiled. Here, we will focus on mesenchymal stem cells and review the main mechanisms involved in adipo, chondro and osteogenesis, discussing how the extracellular matrix can impact not only lineage commitment, but, also, their survival and potentiality. This review critically analyzes recent work in the field in an effort towards a better understanding of the roles of Matrix Metalloproteinases and their inhibitors in the above-cited events.

The cJUN NH2-terminal kinase (JNK) pathway contributes to mouse mammary gland remodeling during involution

Involution returns the lactating mammary gland to a quiescent state after weaning. The mechanism of involution involves collapse of the mammary epithelial cell compartment. To test whether the cJUN NH₂-terminal kinase (JNK) signal transduction pathway contributes to involution, we established mice with JNK deficiency in the mammary epithelium. We found that JNK is required for efficient involution. JNK deficiency did not alter the STAT3/5 or SMAD2/3 signaling pathways that have been previously implicated in this process. Nevertheless, JNK promotes the expression of genes that drive involution, including matrix metalloproteases, cathepsins, and BH3-only proteins. These data demonstrate that JNK has a key role in mammary gland involution post lactation.

Anatomical, Physiological, and Functional Diversity of Adipose Tissue

Adipose tissue depots can exist in close association with other organs, where they assume diverse, often non-traditional functions. In stem cell-rich skin, bone marrow, and mammary glands, adipocytes signal to and modulate organ regeneration and remodeling. Skin adipocytes and their progenitors signal to hair follicles, promoting epithelial stem cell quiescence and activation, respectively. Hair follicles signal back to adipocyte progenitors, inducing their expansion and regeneration, as in skin scars. In mammary glands and heart, adipocytes supply lipids to neighboring cells for nutritional and metabolic functions, respectively. Adipose depots adjacent to skeletal structures function to absorb mechanical shock. Adipose tissue near the surface of skin and intestine senses and responds to bacterial invasion, contributing to the body's innate immune barrier. As the recognition of diverse adipose depot functions increases, novel therapeutic approaches centered on tissue-specific adipocytes are likely to emerge for a range of cancers and regenerative, infectious, and autoimmune disorders.

Mammary Gland Involution Provides a Unique Model to Study the TGF-β Cancer Paradox

Transforming Growth Factor-β (TGF-β) signaling in cancer has been termed the “TGF-β paradox”, acting as both a tumor suppresser and promoter. The complexity of TGF-β signaling within the tumor is context dependent, and greatly impacted by cellular crosstalk between TGF-β responsive cells in the microenvironment including adjacent epithelial, endothelial, mesenchymal, and hematopoietic cells. Here we utilize normal, weaning-induced mammary gland involution as a tissue microenvironment model to study the complexity of TGF-β function. This article reviews facets of mammary gland involution that are TGF-β regulated, namely mammary epithelial cell death, immune activation, and extracellular matrix remodeling. We outline how distinct cellular responses and crosstalk between cell types during physiologically normal mammary gland involution contribute to simultaneous tumor suppressive and promotional microenvironments. We also highlight alternatives to direct TGF-β blocking anti-cancer therapies with an emphasis on eliciting concerted microenvironmental-mediated tumor suppression.

High-fat diet-induced obesity regulates MMP3 to modulate depot- and sex-dependent adipose expansion in C57BL/6J mice

Increased adipocyte size is hypothesized to signal the recruitment of adipose progenitor cells (APCs) to expand tissue storage capacity. To investigate depot and sex differences in adipose growth, male and female C57BL/6J mice (10 wk-old) were challenged with high-fat (HF) or low-fat (LF) diets (D) for 14 wk. The HFD increased gonadal (GON) depot weight by adipocyte hypertrophy and hyperplasia in females but hypertrophy alone in males. In both sexes, inguinal (ING) adipocytes were smaller than GON, and depot expansion was due to hypertrophy. Matrix metalloproteinase 3 (Mmp3), an antiadipogenic factor, and its inhibitor Timps modulate the extracellular matrix remodeling needed for depot expansion. Mmp3 mRNA was depot different (ING > GON), higher in females than males and mainly expressed in APCs. In males, HFD-induced obesity increased tissue and APC Mmp3 mRNA levels and MMP3 protein and enzymatic activity. In females however, HFD significantly decreased MMP3 protein without affecting its mRNA levels. MMP3 activity also decreased (significant in ING). Timp4 mRNA was expressed mainly in adipocytes, and HFD-induced obesity tended to increase the ratio of TIMP4 to MMP3 protein in females, whereas it decreased it in males. Overexpression of Mmp3 in 3T3-L1 preadipocytes or rhMMP3 protein added to primary human preadipocytes inhibited differentiation, whereas rhTIMP4 improved adipogenesis and attenuated the inhibitory effect of rhMMP3. These data suggest that HFD-induced obesity downregulates APC MMP3 expression to trigger adipogenesis, and adipocyte TIMP4 may modulate this process to regulate hyperplastic vs. hypertrophic adipose tissue expansion, fat distribution, and metabolic health in a sex- and depot-dependent manner.

Adipocyte-secreted chemerin is processed to a variety of isoforms and influences MMP3 and chemokine secretion through an NFkB-dependent mechanism

Obesity is associated with white adipose tissue (WAT) remodelling characterized by changes in cellular composition, size, and adipokine secretion. Levels of the adipokine chemerin are positively associated with obesity; however, the biological function of chemerin in WAT is poorly understood. We identified factors involved in WAT remodelling, including matrix metalloproteinase (Mmp)3 and chemokines (Ccl2, 3, 5, 7), as novel targets of chemerin signalling in mature adipocytes. Inhibition of chemerin signalling increased MMP activity and the recruitment of macrophages towards adipocyte-conditioned media. These effects were mediated through increases in NFkB signalling, suggesting that chemerin exerts an anti-inflammatory influence. We also demonstrate that multiple chemerin isoforms are present in adipocyte-conditioned media and that adipocyte-secreted chemerin, but not synthetic chemerin, recapitulates the activity of endogenous chemerin. Considered altogether, this suggests that endogenously secreted chemerin plays an autocrine/paracrine role in WAT, identifying chemerin as a therapeutic target to modulate adipose remodelling.

Deciphering Pro-Lymphangiogenic Programs during Mammary Involution and Postpartum Breast Cancer

Postpartum breast cancers are a highly metastatic subset of young women’s breast cancers defined as breast cancers diagnosed in the postpartum period or within 5 years of last child birth. Women diagnosed with postpartum breast cancer are nearly twice as likely to develop metastasis and to die from breast cancer when compared with nulliparous women. Additionally, epidemiological studies utilizing multiple cohorts also suggest that nearly half of all breast cancers in women aged <45 qualify as postpartum cases. Understanding the biology that underlies this increased risk for metastasis and death may lead to identification of targeted interventions that will benefit the large number of young women with breast cancer who fall into this subset. Preclinical mouse models of postpartum breast cancer have revealed that breast tumor cells become more aggressive if they are present during the normal physiologic process of postpartum mammary gland involution in mice. As involution appears to be a period of lymphatic growth and remodeling, and human postpartum breast cancers have high peritumor lymphatic vessel density (LVD) and increased incidence of lymph node metastasis (1, 2), we propose that novel insight into is to be gained through the study of the biological mechanisms driving normal postpartum mammary lymphangiogenesis as well as in the microenvironment of postpartum tumors.

Proteolytic receptor cleavage in the pathogenesis of blood rheology and co-morbidities in metabolic syndrome. Early forms of autodigestion

Abnormal blood rheological properties seldom occur in isolation and instead are accompanied by other complications, often designated as co-morbidities. In the metabolic syndrome with complications like hypertension, diabetes and lack of normal microvascular blood flow, the underlying molecular mechanisms that simultaneously lead to elevated blood pressure and diabetes as well as abnormal microvascular rheology and other cell dysfunctions have remained largely unknown. In this review, we propose a new hypothesis for the origin of abnormal cell functions as well as multiple co-morbidities. Utilizing experimental models for the metabolic disease with diverse co-morbidities we summarize evidence for the presence of an uncontrolled extracellular proteolytic activity that causes ectodomain receptor cleavage and loss of their associated cell function. We summarize evidence for unchecked degrading proteinase activity, e.g. due to matrix metalloproteases, in patients with hypertension, Type II diabetes and obesity, in addition to evidence for receptor cleavage in the form of receptor fragments and decreased extracellular membrane expression levels. The evidence suggest that a shift in blood rheological properties and other co-morbidities may in fact be derived from a common mechanism that is due to uncontrolled proteolytic activity, i.e. an early form of autodigestion. Identification of the particular proteases involved and the mechanisms of their activation may open the door to treatment that simultaneously targets multiple co-morbidities in the metabolic syndrome.

Tissue inhibitor of metalloproteases-4 (TIMP-4) modulates adipocyte differentiation in vitro

Tissue inhibitors of metalloproteases (TIMPs) are multifunctional proteins that inhibit matrix metalloproteases (MMPs). The latest described member of the family, TIMP-4, is expressed mainly in adipose tissue, with detectable levels in the brain and heart. Besides its high expression in fat, the role of this inhibitor in adipose tissue is unknown. In order to study the role of TIMP-4 during adipogenesis in vitro, 3T3-L1 cells were stably transfected with a TIMP-4 specific shRNA or a control shRNA. Unexpectedly, upon TIMP-4 knockdown, 3T3-L1 cells differentiated faster into mature adipocytes. To get better insight of TIMP-4's role in adipogenesis, microarray expression analyses were performed. Network enrichment analyses uncovered 25 significant upstream signaling pathways, among which the NFκB cascade was found. Previous works have shown that NFκB is a key regulator of adipogenesis. In accordance, we found that TIMP-4 knockdown decreased NFκB activity during adipogenesis. The present work suggests that TIMP-4 might act as a negative regulator of adipogenesis through NFκB cascade modulation.

Deletion of phospholipase A2 group IVc induces apoptosis in rat mammary tumour cells by the nuclear factor-κB/lipocalin 2 pathway

Although some forms of phospholipase A2, the initiator of the arachidonic acid cascade, contribute to carcinogenesis in many organs, the contribution of phospholipase A2 group IVc (Pla2g4c) remains to be clarified and the function of the enzyme in cancer development is unknown. The Hirosaki hairless rat (HHR), a mutant rat strain with autosomal recessive inheritance, derived spontaneously from the Sprague-Dawley rat (SDR). The HHRs showed a lower incidence and much smaller volume of mammary tumours induced by 7,12-dimethylbenz[a]anthracene, and a markedly increased number of TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling)-positive apoptotic cells was detected. Array comparative genomic hybridization and PCR analyses revealed the deletion of 50-kb genomic DNA on 1q21, including Pla2g4c, in HHRs. The Pla2g4c gene was expressed in the ductal carcinoma cells and myoepithelial cells in SDRs, but not in HHRs. The direct involvement of Pla2g4c in the prevention of cell death was demonstrated through the inhibition of its expression in rat mammary tumour RMT-1 cells using siRNA. This treatment also induced expression of lipocalin 2 (Lcn2) and other NF-κB (nuclear factor κB)-related genes. siRNA-induced apoptosis was inhibited by Lcn2 repression or NF-κB inhibitors. This is the first report on Pla2g4c gene-deficient rats and their low susceptibility to mammary carcinogenesis by enhancing NF-κB/Lcn2-induced apoptosis.

Mammary gland development: cell fate specification, stem cells and the microenvironment

The development of the mammary gland is unique: the final stages of development occur postnatally at puberty under the influence of hormonal cues. Furthermore, during the life of the female, the mammary gland can undergo many rounds of expansion and proliferation. The mammary gland thus provides an excellent model for studying the ‘stem/progenitor’ cells that allow this repeated expansion and renewal. In this Review, we provide an overview of the different cell types that constitute the mammary gland, and discuss how these cell types arise and differentiate. As cellular differentiation cannot occur without proper signals, we also describe how the tissue microenvironment influences mammary gland development.

Regulation of epithelial-mesenchymal transition in breast cancer cells by cell contact and adhesion

Epithelial-mesenchymal transition (EMT) is a physiological program that is activated during cancer cell invasion and metastasis. We show here that EMT-related processes are linked to a broad and conserved program of transcriptional alterations that are influenced by cell contact and adhesion. Using cultured human breast cancer and mouse mammary epithelial cells, we find that reduced cell density, conditions under which cell contact is reduced, leads to reduced expression of genes associated with mammary epithelial cell differentiation and increased expression of genes associated with breast cancer. We further find that treatment of cells with matrix metalloproteinase-3 (MMP-3), an inducer of EMT, interrupts a defined subset of cell contact-regulated genes, including genes encoding a variety of RNA splicing proteins known to regulate the expression of Rac1b, an activated splice isoform of Rac1 known to be a key mediator of MMP-3-induced EMT in breast, lung, and pancreas. These results provide new insights into how MMPs act in cancer progression and how loss of cell-cell interactions is a key step in the earliest stages of cancer development.

The type 7 serotonin receptor, 5-HT 7 , is essential in the mammary gland for regulation of mammary epithelial structure and function

Autocrine-paracrine activity of serotonin (5-hydroxytryptamine, 5-HT) is a crucial homeostatic parameter in mammary gland development during lactation and involution. Published studies suggested that the 5-HT₇ receptor type was important for mediating several effects of 5-HT in the mammary epithelium. Here, using 5-HT₇ receptor-null (HT7KO) mice we attempt to understand the role of this receptor in mediating 5-HT actions within the mammary gland. We demonstrate for the first time that HT7KO dams are inefficient at sustaining their pups. Histologically, the HT7KO mammary epithelium shows a significant deviation from the normal secretory epithelium in morphological architecture, reduced secretory vesicles, and numerous multinucleated epithelial cells with atypically displaced nuclei, during lactation. Mammary epithelial cells in HT7KO dams also display an inability to transition from lactation to involution as normally seen by transition from a columnar to a squamous cell configuration, along with alveolar cell apoptosis and cell shedding. Our results show that 5-HT₇ is required for multiple actions of 5-HT in the mammary glands including core functions that contribute to changes in cell shape and cell turnover, as well as specialized secretory functions. Understanding these actions may provide new interventions to improve lactation performance and treat diseases such as mastitis and breast cancer.

Temporal trends in the inflammatory cytokine profile of human breastmilk

A longer lifetime duration of breastfeeding may decrease the risk of breast cancer by reducing breast inflammation and mitigating inflammatory cytokine expression during postlactational involution. However, little is known about how the inflammatory cytokine profile in human breastmilk changes over time. To study temporal trends in breastmilk cytokine expression, we measured 80 human cytokines in the whey fraction of breastmilk samples from 15 mothers at 1, 4, 8, and 12 weeks postpartum. We used mixed models to identify temporal changes in cytokine expression and investigated parity status (multiparous vs. primiparous) as a potential confounder. Nine cytokines (monocyte chemoattractant protein-1, epithelial-derived neutrophil-activating protein-78, hepatocyte growth factor, insulin-like growth factor-binding protein-1, interleukin-16, interleukin-8, macrophage colony-stimulating factor, osteoprotegerin, and tissue inhibitor of metallopeptidase-2) had significantly decreased expression with increasing breastfeeding duration; all nine have known roles in breast involution, inflammation, and cancer and may serve as biomarkers of changing breast microenvironment. No cytokine significantly increased in level over the study period. Total protein concentration significantly decreased over time (p<0.0001), which may mediate the association between length of breastfeeding and inflammatory cytokine expression. Parity status did not confound temporal trends, but levels of several cytokines were significantly higher among multiparous versus primiparous women. Our results suggest that inflammatory cytokine expression during lactation is dynamic, and expressed milk may provide a noninvasive window into the extensive biological changes that occur in the postpartum breast.

Macrophage metalloelastase (MMP12) regulates adipose tissue expansion, insulin sensitivity, and expression of inducible nitric oxide synthase

Macrophage metalloelastase, a matrix metallopeptidase (MMP12) predominantly expressed by mature tissue macrophages, is implicated in pathological processes. However, physiological functions for MMP12 have not been described. Because mRNA levels for the enzyme increase markedly in adipose tissue of obese mice, we investigated the role of MMP12 in adipose tissue expansion and insulin resistance. In humans, MMP12 expression correlated positively and significantly with insulin resistance, TNF-α expression, and the number of CD14(+)CD206(+) macrophages in adipose tissue. MMP12 was the most abundant matrix metallopeptidase detected by proteomic analysis of conditioned medium of M2 macrophages and dendritic cells. In contrast, it was detected only at low levels in bone marrow derived macrophages and M1 macrophages. When mice received a high-fat diet, adipose tissue mass increased and CD11b(+)F4/80(+)CD11c(-) macrophages accumulated to a greater extent in MMP12-deficient (Mmp12(-/-)) mice than in wild-type mice (Mmp12(+/+)). Despite being markedly more obese, fat-fed Mmp12(-/-) mice were more insulin sensitive than fat-fed Mmp12(+/+) mice. Expression of inducible nitric oxide synthase (Nos2) by Mmp12(-/-) macrophages was significantly impaired both in vivo and in vitro, suggesting that MMP12 might mediate nitric oxide production during inflammation. We propose that MMP12 acts as a double-edged sword by promoting insulin resistance while combatting adipose tissue expansion.

Cleavage of Histone 3 by Cathepsin D in the involuting mammary gland

The post-lactational regression of mammary gland is a complex multi-step process designed to conserve the biological function of the gland for next pregnancy. This developmental stage is a biological intrigue with great relevance to breast cancer research, and thus has been the subject of intensive scrutiny. Multipronged studies (microarray, proteomics profiling, animal knock-out models) have provided a repertoire of genes critical to involution. However, the caveat of these approaches remains in their failure to reveal post-translational modification(s), an emerging and critical aspect of gene regulation in developmental processes and mammary gland remodeling. The massive surge in the lysosomal enzymes concurrent with the onset of involution has been known for decades, and considered essential for “clearance” purposes. However, functional significance of these enzymes in diverse biological processes distinct from their proteolytic activity is just emerging. Studies from our laboratory had indicated specific post-translational modifications of the aspartyl endopeptidase Cathepsin D (CatD) at distinct stages mammary gland development. This study addresses the biological significance of these modifications in the involution process, and reveals that post-translational modifications drive CatD into the nucleus to cleave Histone 3. The cleavage of Histone 3 has been associated with cellular differentiation and could be critical instigator of involution process. From functional perspective, deregulated expression and increased secretion of CatD are associated with aggressive and metastatic phenotype of breast cancer. Thus unraveling CatD’s physiological functions in mammary gland development will bridge the present gap in understanding its pro-tumorigenic/metastatic functions, and assist in the generation of tailored therapeutic approaches.

Macrophages and the regulation of adipose tissue remodeling

The ability of adipose tissue to adapt to a changing nutrient environment is critical to the maintenance of metabolic control. Nutrient excess and deficiency alter the shape of adipose tissue drastically and trigger many events that are collectively known as adipose tissue remodeling. Remodeling of adipose tissue involves more than adipocytes and is controlled by an extensive network of stromal cells and extracellular matrix proteins. Prominent players in this process are adipose tissue macrophages, which are a specialized leukocyte present in lean and obese states that contributes to adipose tissue inflammation. The interest in adipose tissue remodeling has been accelerated by the current epidemic of obesity and the chronic generation of signals that lead to expansion of adipose tissue. It is clear that evidence of dysfunctional remodeling events is a hallmark of obesity associated with metabolic disease. This review summarizes and highlights the recent work in this area and provides a framework in which to consider how adipose tissue macrophages contribute to the remodeling events in lean and obese states. Advancing our understanding of the involvement of macrophages in adipose tissue remodeling will promote one aspect of the new field of "immunometabolism," which connects control systems developed for regulation of immunity with those that control metabolism. It will also provide insight into how physiologic and pathophysiologic remodeling differs in adipose tissue and identify potential nodes for intervention to break the link between obesity and disease.

Gelatinase B (MMP-9) gene silencing does not affect murine preadipocyte differentiation

Growth of adipose tissue involves differentiation of preadipocytes into mature lipid-containing adipocytes. The matrix metalloproteinases (MMPs) are known regulators of adipose tissue biology, and previous studies suggested a key role for gelatinase B (MMP-9) in adipogenesis. In the present study we have evaluated a potential functional role of MMP-9 by performing gene silencing in 3T3-F442A preadipocytes. At the end of a 12-day differentiation period, no significant differences were observed between MMP-9 knockdown cells and the control cells with respect to intracytoplasmatic lipid content, or expression of the adipogenic markers aP2, PPARγ, Lpl, and adiponectin, or of the preadipocyte marker Pref-1. Thus, in vitro differentiation of 3T3-F442A preadipocytes into mature adipocytes is not significantly affected by the loss of MMP-9.

Peanut sprout ethanol extract inhibits the adipocyte proliferation, differentiation, and matrix metalloproteinases activities in mouse fibroblast 3T3-L1 preadipocytes

3T3-L1 preadipocyte were differentiated to adipocytes, and then treated with 0, 10, 20, and 40 µg/mL of peanut sprout ethanol extract (PSEE). The main component of PSEE is resveratrol which contained 5.55 mg/mL of resveratrol. The MTT assay, Oil-Red O staining, glycerol-3-phosphate dehydrogenase (GPDH) activity, and the triglyceride concentration were determined in 3T3-L1 cells. MMP-2 and MMP-9 activities as well as mRNA expressions of C/EBP β and C/EBP α were also investigated. As the concentration of PSEE in adipocytes increased, the cell proliferation was decreased in a dose-dependent manner from 4 days of incubation (P < 0.05). The GDPH activity (P < 0.05) and the triglyceride concentration (P < 0.05) were decreased as the PSEE treatment concentration increased. The mRNA expression of C/EBPβ in 3T3-L1 cells was significantly low in groups of PSEE-treated, compared with control group (P < 0.05). The MMP-9 (P < 0.05) and MMP-2 (P < 0.05) activities were decreased in a dose-dependent manner as the PSEE concentration increased from 20 µg/mL. In conclusion, it was found that PSEE has an effect on restricting proliferation and differentiation of adipocytes.

Adipose tissue plasticity from WAT to BAT and in between

Adipose tissue plays an essential role in regulating energy balance through its metabolic, cellular and endocrine functions. Adipose tissue has been historically classified into anabolic white adipose tissue and catabolic brown adipose tissue. An explosion of new data, however, points to the remarkable heterogeneity among the cells types that can become adipocytes, as well as the inherent metabolic plasticity of mature cells. These data indicate that targeting cellular and metabolic plasticity of adipose tissue might provide new avenues for treatment of obesity-related diseases. This review will discuss the developmental origins of adipose tissue, the cellular complexity of adipose tissues, and the identification of progenitors that contribute to adipogenesis throughout development. We will touch upon the pathological remodeling of adipose tissue and discuss how our understanding of adipose tissue remodeling can uncover new therapeutic targets. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.