ErbB2 and EGFR are downmodulated during the differentiation of 3T3-L1 preadipocytes

M2 macrophages independently promote beige adipogenesis via blocking adipocyte Ets1

Adipose tissue macrophages can promote beige adipose thermogenesis by altering local sympathetic activity. Here, we perform sympathectomy in mice and further eradicate subcutaneous adipose macrophages and discover that these macrophages have a direct beige-promoting function that is independent of sympathetic system. We further identify adipocyte Ets1 as a vital mediator in this process. The anti-inflammatory M2 macrophages suppress Ets1 expression in adipocytes, transcriptionally activate mitochondrial biogenesis, as well as suppress mitochondrial clearance, thereby increasing the mitochondrial numbers and promoting the beiging process. Male adipocyte Ets1 knock-in mice are completely cold intolerant, whereas male mice lacking Ets1 in adipocytes show enhanced energy expenditure and are resistant to metabolic disorders caused by high-fat-diet. Our findings elucidate a direct communication between M2 macrophages and adipocytes, and uncover a function for Ets1 in responding to macrophages and negatively governing mitochondrial content and beige adipocyte formation.

EGFR-mediated activation of adipose tissue macrophages promotes obesity and insulin resistance

Obesity and obesity-related health complications are increasing in prevalence. Adipose tissue from obese subjects has low-grade, chronic inflammation, leading to insulin resistance. Adipose tissue macrophages (ATMs) are a source of proinflammatory cytokines that further aggravate adipocyte dysfunction. In response to a high fat diet (HFD), ATM numbers initially increase by proliferation of resident macrophages, but subsequent increases also result from infiltration in response to chemotactic signals from inflamed adipose tissue. To elucidate the underlying mechanisms regulating the increases in ATMs and their proinflammatory phenotype, we investigated the role of activation of ATM epidermal growth factor receptor (EGFR). A high fat diet increased expression of EGFR and its ligand amphiregulin in ATMs. Selective deletion of EGFR in ATMs inhibited both resident ATM proliferation and monocyte infiltration into adipose tissue and decreased obesity and development of insulin resistance. Therefore, ATM EGFR activation plays an important role in adipose tissue dysfunction.

Neuregulin 4 Downregulation Induces Insulin Resistance in 3T3-L1 Adipocytes through Inflammation and Autophagic Degradation of GLUT4 Vesicles

The adipokine Neuregulin 4 (Nrg4) protects against obesity-induced insulin resistance. Here, we analyze how the downregulation of Nrg4 influences insulin action and the underlying mechanisms in adipocytes. Validated shRNA lentiviral vectors were used to generate scramble (Scr) and Nrg4 knockdown (KD) 3T3-L1 adipocytes. Adipogenesis was unaffected in Nrg4 KD adipocytes, but there was a complete impairment of the insulin-induced 2-deoxyglucose uptake, which was likely the result of reduced insulin receptor and Glut4 protein. Downregulation of Nrg4 enhanced the expression of proinflammatory cytokines. Anti-inflammatory agents recovered the insulin receptor, but not Glut4, content. Proteins enriched in Glut4 storage vesicles such as the insulin-responsive aminopeptidase (IRAP) and Syntaxin-6 as well as TBC1D4, a protein involved in the intracellular retention of Glut4 vesicles, also decreased by Nrg4 KD. Insulin failed to reduce autophagy in Nrg4 KD adipocytes, observed by a minor effect on mTOR phosphorylation, at the time that proteins involved in autophagy such as LC3-II, Rab11, and Clathrin were markedly upregulated. The lysosomal activity inhibitor bafilomycin A1 restored Glut4, IRAP, Syntaxin-6, and TBC1D4 content to those found in control adipocytes. Our study reveals that Nrg4 preserves the insulin responsiveness by preventing inflammation and, in turn, benefits the insulin regulation of autophagy.

C1q/TNF-Related Protein 3 (CTRP-3) Deficiency of Adipocytes Affects White Adipose Tissue Mass but Not Systemic CTRP-3 Concentrations

CTRP-3 (C1q/TNF-related protein-3) is an adipokine with endocrine and immunological function. The impact of adipocyte CTRP-3 production on systemic CTRP-3 concentrations and on adipocyte biology is unknown. A murine model of adipocyte CTRP-3 knockout (KO) was established (via the Cre/loxP system). Serum adipokine levels were quantified by ELISA and adipose tissue (AT) gene expression by real-time PCR. Preadipocytes were isolated from AT and differentiated into adipocytes. Comparative transcriptome analysis was applied in adipocytes and liver tissue. Body weight and AT mass were reduced in CTRP-3 KO mice together with decreased serum leptin. In primary cells from visceral AT of KO mice, expression of adiponectin, progranulin, and resistin was induced, while peroxisome proliferator activated receptor γ (PPARγ) was decreased. M1/M2 macrophage polarization markers were shifted to a more anti-inflammatory phenotype. CTRP-3 expression in AT did not contribute to serum concentrations. AT and liver morphology remained unaffected by CTRP-3 KO. Myelin transcription factor 1-like (Myt1l) was identified as a highly upregulated gene. In conclusion, adipocyte CTRP-3 has a role in adipogenesis and AT weight gain whereas adipocyte differentiation is not impaired by CTRP-3 deficiency. Since no effects on circulating CTRP-3 levels were observed, the impact of adipocyte CTRP-3 KO is limited to adipose tissue. Modified AT gene expression indicates a rather anti-inflammatory phenotype.

Characterization of 7A7, an anti-mouse EGFR monoclonal antibody proposed to be the mouse equivalent of cetuximab

The Epidermal Growth Factor Receptor (EGFR) is selectively expressed on the surface of numerous tumours, such as non-small cell lung, ovarian, colorectal and head and neck carcinomas. EGFR has therefore become a target for cancer therapy. Cetuximab is a chimeric human/mouse monoclonal antibody (mAb) that binds to EGFR, where it both inhibits signaling and induces cell death by antibody-dependent cell mediated cytotoxicity (ADCC). Cetuximab has been approved for clinical use in patients with head and neck squamous cell carcinoma (HNSCC) and colorectal cancer. However, only 15-20% patients benefit from this drug, thus new strategies to improve cetuximab efficiency are required. We aimed to develop a reliable and easy preclinical mouse model to evaluate the efficacy of EGFR-targeted antibodies and examine the immune mechanisms involved in tumour regression. We selected an anti-mouse EGFR mAb, 7A7, which has been reported to be "mouse cetuximab" and to exhibit similar properties to its human counterpart. Unfortunately, we were unable to reproduce previous results obtained with the 7A7 mAb. In our hands, 7A7 failed to recognize mouse EGFR, both in native and reducing conditions. Moreover, in vivo administration of 7A7 in an EGFR-expressing HPV38 tumour model did not have any impact on tumour regression or animal survival. We conclude that 7A7 does not recognize mouse EGFR and therefore cannot be used as the mouse equivalent of cetuximab use in humans. As a number of groups have spent effort and resources with similar issues we feel that publication is a responsible approach.

EGFR/ERBB receptors differentially modulate sebaceous lipogenesis

The roles of the epidermal growth factor receptor (EGFR) in sebaceous glands remain poorly explored. We show that human sebocytes express EGFR and lower levels of ERBB2 and ERBB3, all receptors being downregulated after the induction of lipid synthesis. Nile red staining showed that siRNA-mediated downregulation of EGFR or ERBB3 increases lipid accumulation, whereas ERBB2 downregulation has no effect. Spectrometry confirmed induction of triglycerides after EGFR or ERBB3 downregulation and revealed induction of cholesteryl esters after downregulation of EGFR, ERBB2 or ERBB3. Thus, EGFR/ERBB receptors differentially modulate sebaceous lipogenesis, a key feature of sebaceous gland physiology and of several skin diseases.

The use of Transwells™ improves the rates of differentiation and growth of cultured 3T3L1 cells

The use of Transwells™ for routine cultures of 3T3L1 cells results in a much improved rate of differentiation of fibroblasts to adipocytes (100% in 9 of 10 tests) compared with bottom-well layer cultures. Mean size of cells was not different, but the cell number and overall cell mass was 3× larger in transwell in spite of a smaller surface area. The difference between both models was the accessibility in transwells of both sides of the cells to the medium (and oxygen). Cells were counted, and their size estimated using a handheld cell counter, Scepter™, designed for blood cells, but adjusted to the larger size of adipocytes. Finally, the effect of nitric oxide was tested using spermineNONOate, a nitric oxide (NO·) donor. The product was released to cultures at a constant 1 μl/h rate for up to 3 days using osmotic Alzet™ minipumps held in wells with water and discharging their contents to the cultured cell-laden wells through a short capillary tube. A rate of 0.3 pmol/min/ml of medium did not affect the cells' size, but 0.4 pmol/min/ml significantly increased cell mass. The methodological improvements presented here allow for more uniform cultured cell yields and a more flexible environment for control of cell size and administration of signaling agents.

Breast reconstruction with autologous fat graft mixed with platelet-rich plasma

BACKGROUND

The purpose of this study was to review the authors' experience of fat grafting, evaluating the effects related to the use of fat grafting with platelet-rich plasma (PRP) in the improvement of fat volume in breast reconstruction and comparing the results with a control group (only centrifuged fat grafting).

METHODS

A total of 50 patients aged between 19 and 60 years affected by breast soft-tissue defects were analyzed at the Plastic and Reconstructive Department of the University of Tor Vergata. They were treated with fat grafting + PRP. The control group (50 patients with breast soft-tissue defects) were treated with centrifuged fat grafting injection according to Coleman's procedure.

RESULTS

The patients treated with PRP added to the autologous fat grafts showed a 69% maintenance of the contour restoring and of 3-dimensional volume after 1 year, whereas the patients of the control group treated with centrifuged fat grafting showed a 39% maintenance.

CONCLUSION

PRP mixed with fat grafting leads to an improvement in maintaining breast volume in patients affected by breast soft-tissue defects.

Platelet-rich plasma greatly potentiates insulin-induced adipogenic differentiation of human adipose-derived stem cells through a serine/threonine kinase Akt-dependent mechanism and promotes clinical fat graft maintenance

The potential plasticity and therapeutic utility in tissue regeneration of human adipose-derived stem cells (ASCs) isolated from adult adipose tissue have recently been highlighted. The use of autologous platelet-rich plasma (PRP) represents an alternative strategy in regenerative medicine for the local release of multiple endogenous growth factors. Here we investigated the signaling pathways and effects of PRP and human recombinant insulin on proliferation and adipogenic differentiation of ASCs in vitro. PRP stimulated proliferation (EC(50) = 15.3 ± 1.3% vol/vol), whereas insulin's effect was the opposite (IC(50) = 3.0 ± 0.5 μM). Although PRP alone did not increase adipogenesis, in association with insulin it prevented ASC proliferative arrest, greatly enhanced intracytoplasmic lipid accumulation, strongly increased serine/threonine kinase Akt phosphorylation and mouse monoclonal anti-sterol regulatory element binding protein-1 accumulation, and downregulated Erk-1 activity; adipogenic effects were markedly prevented by the Akt inhibitor wortmannin. PRP with insulin synergistically upregulated fibroblast growth factor receptor (FGFR) and downregulated epidermal growth factor receptor (ErbB) expression; moreover, PRP in association prevented insulin-induced insulin-like growth factor-1 receptor and insulin receptor downregulation. The inhibition of FGFR-1, epidermal growth factor receptor (EGFR), and epidermal growth factor receptor-2 (ErbB2) activity reduced ASC proliferation, but only that of FGFR-1 reduced adipogenesis and Akt phosphorylation, whereas the ErbB2 inhibition effects were the opposite. However, EGFR activity was needed for ErbB2-mediated inhibition of ASC adipogenesis. Clinically, the injection of insulin further ameliorated patients' 1-year PRP-induced fat graft volume maintenance and contour restoring. Our results ascertain that PRP in association with insulin greatly potentiates adipogenesis in human ASCs through a FGFR-1 and ErbB2-regulated Akt mechanism. The ameliorated clinical fat graft maintenance suggests additional useful translational applications of combined PRP-insulin treatment in regenerative medicine.

Developmentally spliced PKCbetaII provides a possible link between mTORC2 and Akt kinase to regulate 3T3-L1 adipocyte insulin-stimulated glucose transport

Functional adipocyte glucose disposal is a key component of global glucose homeostasis. PKCbetaII is involved in rat skeletal muscle cell ISGT. Western blot analysis and real-time PCR revealed 3T3-L1 cells developmentally regulated PKCbeta splicing such that PKCbetaI was downregulated and PKCbetaII was upregulated during the course of differentiation. An initial glucose uptake screen using PKC inhibitor LY379196 pointed to a PKC isozyme other than PKCzeta mediating 3T3-L1 adipocyte ISGT. Subsequent use of PKCbetaII inhibitor CGP53353 pointed to a role for PKCbetaII in ISGT. Western blot analysis showed that CGP53353 specifically inhibited phosphorylation of PKCbetaII Serine 660. Subcellular fractionation and immunofluorescence demonstrated that PKCbetaII regulates GLUT4 translocation. Further Western blot, immunofluorescence and co-immunoprecipitation analysis reveal that PKCbetaII inhibition does not affect mTORC2 activity yet abrogates phosphorylation of Akt Serine 473. PKCbetaII regulates GLUT4 translocation by regulating Akt phosphorylation and thus activity.

The tyrosine kinase receptor HER2 (erbB-2): from oncogenesis to adipogenesis

Recent experimental evidences begin to support the notion that the proto-oncogene HER2 (erbB-2) might unexpectedly function to modulate the adipogenic conversion of preadipocytes. Two opposing scenarios have been proposed, however, to explain the influence of HER2 on adipocyte differentiation. In one hand, down-modulation of HER2 expression and pharmacological reduction of HER2 activity have been related to enhanced adipocyte differentiation. On the contrary, an increased abundance in HER2 has been described in differentiated adipocytes compared with preadipocytes. Considering that expression and activity of the lipogenic enzyme Fatty Acid Synthase (FASN) become up-regulated during adipogenic conversion, we recently hypothesized that a "HER2 --> FASN axis" -a "lipogenic benefit" that has been shown to enhance cancer cell proliferation, survival, chemoresistance and metastasis in biologically aggressive subgroups of breast carcinomas-might also naturally work during the differentiation of preadipocytes. To definitely clarify if the discrepancy between the opposing theories for a role of HER2 during adipocyte differentiation related to the experimental approach utilized to compare the abundance of HER2 in undifferentiated and differentiated adipocytes (i.e., cell lysates containing equivalent protein content versus cell lysates generated from similar cell numbers), we here took advantage of a high content microscopy approach. Using an automated confocal imaging platform, we monitored the expression status of the adipogenic marker FASN and its timing relationship with HER2 not only in individual 3T3-L1 cells but further in whole cultures of 3T3-L1 preadipocytes undergoing adipogenic conversion. Our findings not only confirm a non-oncogenic role for HER2 in the process of adipose differentiation but further suggest that HER2 might represent a previously unrecognized target to manage obesity via the lipogenic enzyme FASN.

Role of epidermal growth factor and ErbB2 receptors in 3T3-L1 adipogenesis

OBJECTIVE

Epidermal growth factor (EGF) stimulates proliferation in 3T3-L1 preadipocytes, but EGF action in differentiation is less clear. EGF promotes differentiation at concentrations <1 nM but inhibits differentiation at higher concentrations, suggesting a dual role in adipogenesis. We hypothesized that differences in EGF receptor activation and downstream signaling mediate distinct biological effects of EGF at low vs. high abundance.

RESEARCH METHODS AND PROCEDURES

We compared the effects of low (0.1 nM) vs. high (10 nM) EGF on the activation of EGF receptors, proximal signaling molecules Src and Shc, and the downstream mitogen-activated protein kinase (MAPK) pathways extracellular regulated kinase (ERK) and p38 in proliferating and differentiated 3T3-L1 cells.

RESULTS

Both low and high EGF activated ERK and p38 in preadipocytes. Src inhibitors PP1 and PP2 blocked ERK and p38 activation by low but not high EGF, and only high EGF increased Shc phosphorylation. Selective inhibition of the EGF receptor (EGFR) with AG1478 blocked ERK and p38 activation at both concentrations; however, selective inhibition of the ErbB2 receptor (EB2R) with AG825 or small interfering RNA (siRNA) blocked low but not high EGF activation of ERK and p38. Coimmunoprecipitation of EGFR with EB2R and Src was observed with low EGF in preadipocytes but at both concentrations in adipocytes. EB2R inhibition during differentiation decreased p38 activity and peroxisome proliferator-activated receptor gamma (PPARgamma) abundance.

DISCUSSION

Our results show that EGFR homodimers mediate action of EGF at high abundance, but at low abundance, EGF promotes differentiation through EGFR/EB2R heterodimer activation of Src and p38. These results may partially explain the observations that high EGF concentrations inhibit, whereas low concentrations support, preadipocyte differentiation.

Global search for chromosomal abnormalities in infiltrating ductal carcinoma of the breast using array-comparative genomic hybridization

Array-comparative genomic hybridization (a-CGH) is a molecular cytogenetic technique for detection of multiple chromosomal abnormalities in genomic DNA samples. Using an a-CGH with 287 probes, we examined 14 cases of breast infiltrating ductal carcinoma (IDCA) that had previously been classified by fluorescent in situ hybridization (FISH) as either human epidermal growth factor receptor-2 positive (HER2+) or HER2- and analyzed the data by hierarchical, K-means, and principal component analyses. The aim of the study was to identify the genetic abnormalities that are present in breast IDCAs and determine if the global status of 287 cytogenetic locations could be used as a more objective method for breast IDCA classification. Concordance between FISH and a-CGH at the HER2 locus was 78.6% (11/14). In general, a-CGH detected more abnormalities in HER2+ cases. In HER 2+ cases, chromosomes 1, 2, 3, 7, 9, 17, and 20 had more regions that showed statistically significant (P < or = 0.01) changes in DNA copy number. Among all the aberrant cytogenetic locations detected, 20q13, 7p12.3 approximately p12.1, and 17q23.2 approximately q25.3, which contain among others, genes for TNFRSF6B, EGFR, and TK1 showed statistically significant gains (P < or = 0.01) in 83, 66.7, and 50% of the HER2+ IDCA cases, respectively. Chromosome location 8q24.12 approximately q24.13 was the only region that showed consistent amplification in approximately 50% of the HER2- cases. Unsupervised hierarchical and K-means cluster analyses and principal component analysis using the DNA copy number status of 287 cytogenetic locations or the 177 cytogenetic locations that showed statistically significant differences revealed a cluster consisting of mainly HER2- IDCA cases. Even though this study demonstrates the usefulness of a-CGH in the rapid identification of aberrant DNA regions in tumor samples, we conclude that an array-CGH with more than 287 probes will be needed for a more precise mapping of DNA aberrations at the global level.