Protease inhibitor treatments reveal specific involvement of matrix metalloproteinase-9 in human adipocyte differentiation

Myostatin increases the expression of matrix metalloproteinase genes to promote preadipocytes differentiation in pigs

ABSTACTMyostatin (MSTN) resulted in reduced backfat thickness in MSTN-knockout (MSTN-KO) pigs, whereas the underlying mechanism remains elusive. In this study, RNA sequencing (RNA-seq) was used to screen differentially expressed genes (DEGs) in porcine fat tissues. We identified 285 DEGs, including 4 adipocyte differentiation-related genes (ADRGs). Matrix Metalloproteinase-2/7 (MMP-2/7), fibronectin (FN), and laminin (LN) were differentially expressed in MSTN-KO pigs compared with wild-type (WT) pigs. To investigate the molecular mechanism, we treated the preadipocytes with siRNA and recombinant MSTN protein. The results indicated that MSTN increased the expression of MMP-2/7/9 and promoted the preadipocyte differentiation. To further validate the effect of MSTN on MMP-2/7/9 expression, we treated MSTN-KO PK15 cells with recombinant MSTN protein and detected the expression of MMP-2/7/9. The data showed that MSTN increases the expression of MMP-2/7/9 in PK15. This study revealed that MSTN promoted preadipocyte differentiation and provided the basis for the mechanism of fatty deposition in pigs.

Adipose Tissue Development Relies on Coordinated Extracellular Matrix Remodeling, Angiogenesis, and Adipogenesis

Despite developing prenatally, the adipose tissue is unique in its ability to undergo drastic growth even after reaching its mature size. This development and subsequent maintenance rely on the proper coordination between the vascular niche and the adipose compartment. In this review, the process of adipose tissue development is broken down to explain (1) the ultrastructural matrix remodeling that is undertaken during simultaneous adipogenesis and angiogenesis, (2) the paracrine crosstalk involved during adipose development, (3) the mechanical regulators involved in adipose growth, and (4) the proteolytic and paracrine oversight for matrix remodeling during adipose development. It is crucial to gain a better understanding of the complex relationships that exist between adipose tissue and the vasculature during tissue development to provide insights into the pathological tissue expansion of obesity and to develop improved soft-tissue reconstruction techniques.

Improved tenderness of beef from bulls supplemented with active dry yeast is related to matrix metalloproteinases and reduced oxidative stress

Supplementing diets with active dry yeast (ADY, Saccharomyces cerevisiae) improves the carcass quality grade of beef cattle and the tenderness of beef. The relevant mechanisms have not been fully elucidated, but may be related to the effect of ADY on oxidative stress and the activity of matrix metalloproteinases (MMPs). To provide further insight into these mechanisms, this study evaluated the influence of ADY supplementation on growth performance, carcass traits, meat quality, concentrations of MMPs in serum (MMP-2, MMP-9 and MMP-13), oxidative stress indices and antioxidant capacity indices in beef cattle. Forty-six crossbred Simmental × Yanbian bulls (∼18 months of age, BW 436 ± 35 kg) participated in a 145-day finishing trial. ADY supplementation significantly improved marbling deposition, intramuscular fat content, and beef tenderness (P < 0.05); altered individual fatty acid proportions in the beef and increased saturated fatty acids while decreasing polyunsaturated fatty acids (P < 0.05); significantly decreased the abundance of reactive oxygen species in serum and meat; significantly increased the level of superoxide dismutase in meat (P < 0.05); tended to increase the level of catalase (P = 0.075) in serum and glutathione reductase (P = 0.066) in meat; and increased the secretion of MMPs. The improvement of beef tenderness following ADY supplementation of finishing bulls is related to the effects of ADY on the secretion of MMPs and the lowering of oxidative stress.

The Anti-Cancer Properties of the HIV Protease Inhibitor Nelfinavir

Simple Summary

To this day, cancer remains a medical challenge despite the development of cutting-edge diagnostic methods and therapeutics. Thus, there is a continual demand for improved therapeutic options for managing cancer patients. However, novel drug development requires decade-long time commitment and financial investments. Repurposing approved and market-available drugs for cancer therapy is a way to reduce cost and the timeframe for developing new therapies. Nelfinavir is an anti-infective agent that has extensively been used to treat acquired immunodeficiency syndrome (AIDS) in adult and pediatric patients. In addition to its anti-infective properties, nelfinavir has demonstrated potent off-target anti-cancer effects, suggesting that it could be a suitable candidate for drug repurposing for cancer. In this review, we systematically compiled the therapeutic benefits of nelfinavir against cancer as a single drug or in combination with chemoradiotherapy, and outlined the possible underlying mechanistic pathways contributing to the anti-cancer effects.

Abstract

Traditional cancer treatments may lose efficacy following the emergence of novel mutations or the development of chemoradiotherapy resistance. Late diagnosis, high-cost of treatment, and the requirement of highly efficient infrastructure to dispense cancer therapies hinder the availability of adequate treatment in low-income and resource-limited settings. Repositioning approved drugs as cancer therapeutics may reduce the cost and timeline for novel drug development and expedite the availability of newer, efficacious options for patients in need. Nelfinavir is a human immunodeficiency virus (HIV) protease inhibitor that has been approved and is extensively used as an anti-infective agent to treat acquired immunodeficiency syndrome (AIDS). Yet nelfinavir has also shown anti-cancer effects in in vitro and in vivo studies. The anti-cancer mechanism of nelfinavir includes modulation of different cellular conditions, such as unfolded protein response, cell cycle, apoptosis, autophagy, the proteasome pathway, oxidative stress, the tumor microenvironment, and multidrug efflux pumps. Multiple clinical trials indicated tolerable and reversible toxicities during nelfinavir treatment in cancer patients, either as a monotherapy or in combination with chemo- or radiotherapy. Since orally available nelfinavir has been a safe drug of choice for both adult and pediatric HIV-infected patients for over two decades, exploiting its anti-cancer off-target effects will enable fast-tracking this newer option into the existing repertoire of cancer chemotherapeutics.

Differential expression of extracellular matrix and integrin genes in the longissimus thoracis between bulls and steers and their association with intramuscular fat contents

This study was performed to compare expression of genes for extracellular matrix (ECM) components, ECM degrading factors, and integrin subunits in the longissimus thoracis (LT) between bulls and steers. Steers had lower (P<0.05) ECM component collagen type 1 α1 and collagen type 3 α1 mRNA levels than did bulls, but they had higher (P<0.05) thrombospondin 1 mRNA and protein levels. Steers had higher (P<0.01) matrix metalloproteinase (MMP) 9 mRNA levels than did bulls. Steers had higher (P<0.05) integrin α5 mRNA levels but lower (P<0.05) integrin β6 mRNA and protein levels; however, expression levels of several other integrin subunits were not different between steers and bulls. MMP9 mRNA levels were positively correlated (P<0.05) with intramuscular fat content in bull group. In conclusion, these results demonstrate that castration has moderate effects on expression of ECM components, ECM degrading factors, and integrin subunit genes in the LT.

Effects of matrix metalloproteinases on the fate of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have great potential as a source of cells for cell-based therapy because of their ability for self-renewal and differentiation into functional cells. Moreover, matrix metalloproteinases (MMPs) have a critical role in the differentiation of MSCs into different lineages. MSCs also interact with exogenous MMPs at their surface, and regulate the pericellular localization of MMP activities. The fate of MSCs is regulated by specific MMPs associated with a key cell lineage. Recent reports suggest the integration of MMPs in the differentiation, angiogenesis, proliferation, and migration of MSCs. These interactions are not fully understood and warrant further investigation, especially for their application as therapeutic tools to treat different diseases. Therefore, overexpression of a single MMP or tissue-specific inhibitor of metalloproteinase in MSCs may promote transdifferentiation into a specific cell lineage, which can be used for the treatment of some diseases. In this review, we critically discuss the identification of various MMPs and the signaling pathways that affect the differentiation, migration, angiogenesis, and proliferation of MSCs.

TGFβ-induced switch from adipogenic to osteogenic differentiation of human mesenchymal stem cells: identification of drug targets for prevention of fat cell differentiation

BACKGROUND

Patients suffering from osteoporosis show an increased number of adipocytes in their bone marrow, concomitant with a reduction in the pool of human mesenchymal stem cells (hMSCs) that are able to differentiate into osteoblasts, thus leading to suppressed osteogenesis.

METHODS

In order to be able to interfere with this process, we have investigated in-vitro culture conditions whereby adipogenic differentiation of hMSCs is impaired and osteogenic differentiation is promoted. By means of gene expression microarray analysis, we have investigated genes which are potential targets for prevention of fat cell differentiation.

RESULTS

Our data show that BMP2 promotes both adipogenic and osteogenic differentiation of hMSCs, while transforming growth factor beta (TGFβ) inhibits differentiation into both lineages. However, when cells are cultured under adipogenic differentiation conditions, which contain cAMP-enhancing agents such as IBMX of PGE2, TGFβ promotes osteogenic differentiation, while at the same time inhibiting adipogenic differentiation. Gene expression and immunoblot analysis indicated that IBMX-induced suppression of HDAC5 levels plays an important role in the inhibitory effect of TGFβ on osteogenic differentiation. By means of gene expression microarray analysis, we have investigated genes which are downregulated by TGFβ under adipogenic differentiation conditions and may therefore be potential targets for prevention of fat cell differentiation. We thus identified nine genes for which FDA-approved drugs are available. Our results show that drugs directed against the nuclear hormone receptor PPARG, the metalloproteinase ADAMTS5, and the aldo-keto reductase AKR1B10 inhibit adipogenic differentiation in a dose-dependent manner, although in contrast to TGFβ they do not appear to promote osteogenic differentiation.

CONCLUSIONS

The approach chosen in this study has resulted in the identification of new targets for inhibition of fat cell differentiation, which may not only be relevant for prevention of osteoporosis, but also of obesity.

The role of matrix metalloproteinases in muscle and adipose tissue development and meat quality: A review

Matrix metalloproteinases (MMPs) are a group of enzymes that degrade extracellular matrix components but are also important signaling molecules that regulate many biological processes including muscle, adipose and connective tissue development. Most recently it has been discovered that MMPs act as intracellular signaling molecules inducing gene expression and altering related proteins in the nucleus. Several single nucleotide polymorphisms of MMPs and their inhibitors are known to exist and most of the research on MMPs to date has focused on their activity in relation to human health and disease. Nevertheless there is a growing body of evidence identifying important roles of MMPs as regulators of myogenesis, fibrogenesis and adipogenesis. The aim of this review is to highlight the currently known functions of the MMPs that have a direct bearing on the deposition of meat components and their relationship with meat quality. Some central pathways by which these enzymes can affect the tenderness, the amount and type of fatty acids are highlighted.

Role of extracellular matrix in development of skeletal muscle and postmortem aging of meat

The integrity of skeletal muscle is maintained by the intramuscular connective tissues (IMCTs) that are composed of extracellular matrix (ECM) molecules such as collagens, proteoglycans, and glycoproteins. The ECM plays an important role not only in providing biomechanical strength of the IMCT, but also in regulating muscle cell behavior. Some ECM molecules, such as decorin and laminin, modulate the activity of myostatin that regulates skeletal muscle mass. Furthermore, it has been shown that decorin activates Akt downstream of insulin-like growth factor-I receptor (IGF-IR) and enhances the differentiation of myogenic cells, suggesting that decorin acts as a signaling molecule to myogenic cells. With animal growth, the structural integrity of IMCT increases; collagen fibrils within the endomysium associate more closely with each other, and the collagen fibers in the perimysium become increasingly thick and their wavy pattern grows more regular. These changes increase the mechanical strength of IMCT, contributing to the toughening of meat. However, in highly marbled beef cattle like Wagyu, intramuscular fat deposits mainly in the perimysium between muscle fiber bundles during the fattening period. The development of adipose tissues appears to disorganize the structure of IMCT and contributes to the tenderness of Wagyu beef. The IMCT was considered to be rather immutable compared to myofibrils during postmortem aging of meat. However, several studies have shown that collagen networks in the IMCT are disintegrated and proteoglycan components are degraded during postmortem aging. These changes in ECM appear to reduce the mechanical strength of IMCT and contribute to the tenderness of uncooked meat or cooked meat at low temperature. Thus, the ECM plays a multifunctional role in skeletal muscle development and postmortem aging of meat.

Gelatinase A (MMP-2) promotes murine adipogenesis

BACKGROUND

Expansion of adipose tissue is dependent on adipogenesis, angiogenesis and extracellular matrix remodeling. A functional role in these processes was suggested for the gelatinase subfamily of the matrix metalloproteinases. Here, we have evaluated a potential role of gelatinase A (MMP-2) in adipogenesis.

METHODS

Murine embryonic fibroblasts (MEF) were derived from wild-type or MMP-2 deficient mice. Genetic manipulation of Mmp2 (shRNA-knockdown or overexpression) was performed in 3T3-F442A preadipocytes. Cell cultures were subjected to an adipogenic medium. As an in vivo model for de novo adipogenesis, 3T3-F442A preadipocytes with or without knockdown were injected subcutaneously in Nude BALB/c mice kept on high fat diet.

RESULTS

Mmp2 deficient MEF, as compared to controls, showed significantly impaired differentiation into mature adipocytes, as demonstrated by 90% reduced intracellular lipid content and reduced expression of pro-adipogenic markers. Moreover, selective Mmp2 knockdown in 3T3-F442A preadipocytes resulted in significantly reduced differentiation. In contrast, overexpression of Mmp2 resulted in markedly enhanced differentiation. In de novo formed fat pads resulting from preadipocytes with Mmp2 knockdown expression of aP2, Ppar-γ and adiponectin was significantly lower, and collagen was more preserved. The fat pad weights as well as size and density of adipocytes or blood vessels were, however, not significantly different from controls.

CONCLUSION

Our data directly support a functional role of MMP-2 in adipogenesis in vitro, and suggest a potential role in in vivo adipogenesis.

GENERAL SIGNIFICANCE

Selective modulation of MMP-2 levels affects adipogenesis.

Nelfinavir and other protease inhibitors in cancer: mechanisms involved in anticancer activity

OBJECTIVE

To review the mechanisms of anti-cancer activity of nelfinavir and other protease inhibitors (PIs) based on evidences reported in the published literature.

METHODS

We extensively reviewed the literature concerning nelfinavir (NFV) as an off target anti-cancer drug and other PIs. A classification of PIs based on anti-cancer mode of action was proposed. Controversies regarding nelfinavir mode of action were also addressed.

CONCLUSIONS

The two main mechanisms involved in anti-cancer activity are endoplasmic reticulum stress-unfolded protein response pathway and Akt inhibition. However there are many other effects, partially dependent and independent of those mentioned, that may be useful in cancer treatment, including MMP-9 and MMP-2 inhibition, down-regulation of CDK-2, VEGF, bFGF, NF-kB, STAT-3, HIF-1 alfa, IGF, EGFR, survivin, BCRP, androgen receptor, proteasome, fatty acid synthase (FAS), decrease in cellular ATP concentration and upregulation of TRAIL receptor DR5, Bax, increased radiosensitivity, and autophagy. The end result of all these effects is slower growth, decreased angiogenesis, decreased invasion and increased apoptosis, which means reduced proliferation and increased cancer cells death. PIs may be classified according to their anticancer activity at clinically achievable doses, in AKT inhibitors, ER stressors and Akt inhibitors/ER stressors. Beyond the phase I trials that have been recently completed, adequately powered and well-designed clinical trials are needed in the various cancer type settings, and specific trials where NFV is tested in association with other known anti-cancer pharmaceuticals should be sought, in order to find an appropriate place for NFV in cancer treatment. The analysis of controversies on the molecular mechanisms of NFV hints to the possibility that NFV works in a different way in tumor cells and in hepatocytes and adipocytes.

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.

Artemisinic acid is a regulator of adipocyte differentiation and C/EBP δ expression

Adipocyte dysfunction is associated with the development of obesity. In this study, artemisinic acid, which was isolated from Artemisia annua L., inhibited adipogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hAMSCs) and its mechanism of action was determined. The mRNA levels of peroxidase proliferation-activated receptor (PPAR) γ and CCAAT/enhancer binding protein (C/EBP) α, late adipogenic factors, were reduced by artemisinic acid. Moreover, the mRNA levels of the PPAR γ target genes lipoprotein lipase, CD36, adipocyte protein, and liver X receptor were down-regulated by artemisinic acid. Artemisinic acid reduced expression of the C/EBP δ gene without impacting C/EBP β. In addition, attempts to elucidate a possible mechanism underlying the artemisinic acid-mediated effects revealed that reduced expression of the C/EBP δ gene was mediated by inhibiting Jun N-terminal kinase (JNK). Additionally, artemisinic acid also reduced the expression of the adipogenesis-associated genes glucose transporter-4 and vascular endothelial growth factor. In addition to the interference of artemisinic acid with adipogenesis, artemisinic acid significantly attenuated tumor necrosis factor-α-induced secretion of interleukin-6 by undifferentiated hAMSCs, thus influencing insulin resistance and the inflammatory state characterizing obesity. Taken together, these findings indicate that inhibiting adipogenic differentiation of hAMSCs by artemisinic acid occurs primarily through reduced expression of C/EBP δ, which is mediated by the inhibition of JNK and suggest that aremisinic acid may be used as a complementary treatment option for obesity associated with metabolic syndrome.

Chitooligosaccharide ameliorates diet-induced obesity in mice and affects adipose gene expression involved in adipogenesis and inflammation

Chitooligosaccharide (CO) has been reported to have potential antiobestic effects in a few studies, but the antiobesity properties of CO and its related mechanisms in models of dietary obesity remain unclear. We investigated the effect of CO on body weight gain, size of adipocytes, adipokines, and lipid profiles in high-fat (HF) diet-induced obese mice and on the gene expression in adipose tissue using a complementary DNA microarray approach to test the hypothesis that CO supplementation would alleviate HF diet-induced obesity by the alteration of adipose tissue-specific gene expression. Male C57BL/6N mice were fed a normal diet (control), HF diet, or CO-supplemented HF diet (1% or 3%) for 5 months. Compared with the HF diet mice, mice fed the 3% CO-supplemented diet gained 15% less weight but did not display any change in food and energy intake. Chitooligosaccharide supplementation markedly improved serum and hepatic lipid profiles. Histologic examination showed that epididymal adipocyte size was smaller in mice fed the HF + 3% CO. Microarray analysis showed that dietary CO supplementation modulated adipogenesis-related genes such as matrix metallopeptidases 3, 12, 13, and 14; tissue inhibitor of metalloproteinase 1; and cathepsin k in the adipose tissues. Twenty-five percent of the CO-responsive genes identified are involved in immune responses including the inflammatory response and cytokine production. These results suggest that CO supplementation may help ameliorate HF diet-induced weight gain and improve serum and liver lipid profile abnormalities, which are associated, at least in part, with altered adipose tissue gene expression involved in adipogenesis and inflammation.

Stimulation of inflammatory gene expression in human preadipocytes by macrophage-conditioned medium: upregulation of IL-6 production by macrophage-derived IL-1β

The aim of this study was to examine the effects of macrophage secretions on global gene expression in human preadipocytes using microarrays. Preadipocytes were cultured with unconditioned or conditioned medium from U937 macrophages, and gene expression examined with Agilent arrays (43,000 probes). 472 transcripts were differentially regulated (>2-fold difference; P<0.05) between preadipocytes in the conditioned medium compared to the unconditioned; 401 were upregulated and 71 downregulated. The upregulated transcripts were particularly linked to inflammation, including IL-1β, IL-6, and CCL20 (16.8-, 10.0-, and 8.9-fold increases, respectively) together with matrix metalloproteinases (MMP3, MMP9 and MMP12). Major pathways regulated by the conditioned medium were linked to inflammation, macrophage infiltration and lipid accumulation. Network analysis identified NFkB and IL-1β as central nodes in the upregulation of multiple inflammation-related genes. Treatment with an IL-1β neutralising antibody abolished the stimulation of IL-6 secretion by conditioned medium, indicating that IL-1β is a key regulator of preadipocyte IL-6 production. Macrophages evoke extensive changes in preadipocyte gene expression.

Tissue inhibitor of matrix metalloproteinase 1 (TIMP1) controls adipogenesis in obesity in mice and in humans

AIMS/HYPOTHESIS

Extracellular matrix reorganisation is a crucial step of adipocyte differentiation and is controlled by the matrix metalloproteinase-tissue inhibitor of matrix metalloproteinase (TIMP) enzyme system. We therefore sought to define the role of TIMP1 in adipogenesis and to elucidate whether upregulation of TIMP1 in obesity has direct effects on adipocyte formation.

METHODS

TIMP1 protein levels and mRNA were measured in lean and obese mice with a focus on levels in adipose tissue. We also analysed the effect of recombinant murine TIMP1 on adipogenesis, adipocyte size and metabolic control in vitro and in vivo.

RESULTS

TIMP1 levels were increased in the serum and adipose tissue of obese mouse models. Recombinant murine TIMP1 inhibited adipocyte differentiation in 3T3-L1 as well as in subcutaneous primary pre-adipocytes. Conversely, neutralising TIMP1 with a specific antibody enhanced adipocyte differentiation. In vivo, injection of recombinant TIMP1 in mice challenged with a high-fat diet led to enlarged adipocytes. TIMP1-treated mice developed an impaired metabolic profile with increased circulating NEFA levels, hepatic triacylglycerol accumulation and accelerated insulin resistance. Altered glucose clearance in TIMP1-injected mice was due to changes in adipose tissue glucose uptake, whereas muscle glucose clearance remained unaffected.

CONCLUSIONS/INTERPRETATION

TIMP1 is a negative regulator of adipogenesis. In vivo, TIMP1 leads to enlarged adipocytes in the state of overnutrition. This might contribute to the detrimental metabolic consequences seen in TIMP1-injected mice, such as systemic fatty acid overload, hepatic lipid accumulation and insulin resistance.

HIV-protease inhibitors block the replication of both vesicular stomatitis and influenza viruses at an early post-entry replication step

The inhibitors of HIV-1 protease (PIs) have been designed to block the activity of the viral aspartyl-protease. However, it is now accepted that this family of inhibitors can also affect the activity of cell proteases. Since the replication of many virus species requires the activity of host cell proteases, investigating the effects of PIs on the life cycle of viruses other than HIV would be of interest. Here, the potent inhibition induced by saquinavir and nelfinavir on the replication of both vesicular stomatitis and influenza viruses is described. These are unrelated enveloped RNA viruses infecting target cells upon endocytosis and intracellular fusion. The PI-induced inhibition was apparently a consequence of a block at the level of the fusion between viral envelope and endosomal membranes. These findings would open the way towards the therapeutic use of PIs against enveloped RNA viruses other than HIV.

The MMP1 (-16071G/2G) single nucleotide polymorphism associates with the HAART-related lipodystrophic syndrome

OBJECTIVE

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in extracellular matrix remodelling and adipocyte differentiation and are inhibited by antiretrovirals. MMPs and TIMPs and their single nucleotide polymorphisms (SNPs) might contribute to the HAART-related lipodystrophic syndrome pathogenesis.

DESIGN AND SETTING

Cross-sectional study in a university-based outpatient clinic.

PATIENTS AND METHODS

Two hundred and sixteen HIV-infected patients on extended HAART were studied. Serum MMPs (1, 2, 3, 8, 9, 10, 13) and TIMPs (1, 2, 4) were measured by ELISA microarrays. MMP1 (-16071G/2G) SNP was also genotyped. Lipodystrophic syndrome was diagnosed by a clinical scale validated by fat dual energy X-ray absorptiometry.

RESULTS

Eighty-two patients (38.0%) showed lipodystrophic syndrome, mostly lipoatrophy. The 2G/2G MMP1 SNP genotype was more frequent among lipodystrophic syndrome patients (41.3 vs. 20.5%, odds ratio, 2.73; 95% confidence interval, 1.41-5.29; χ² = 9.62, P = 0.002 for HIV-infected patients with and without lipodystrophic syndrome respectively). Carriers of this genotype had higher serum levels of MMP1 compared with those with the 1G/1G (P = 0.02). Higher MMP1 (P = 0.022) and lower TIMP4 (P = 0.038) serum levels were observed while comparing HIV patients with and without lipodystrophic syndrome. MMP1 2G carriage (P = 0.0008), TIMP4 lower serum levels (P = 0.02), treatment with stavudine (P < 0.0001), treatment with zidovudine (P = 0.006) and absence of hepatitis C virus coinfection (P = 0.002) were associated with lipodystrophic syndrome by logistic regression.

CONCLUSION

MMP1 SNP, which induced increased serum levels of this protein, was associated with lipodystrophic syndrome.

An active extract of Lindera obtusiloba inhibits adipogenesis via sustained Wnt signaling and exerts anti-inflammatory effects in the 3T3-L1 preadipocytes

Obesity, the related metabolic syndrome and associated liver diseases represent an epidemic problem and demand for effective therapeutic strategies. In this regard, natural compounds derived from Oriental medicine such as green tea polyphenols influencing adipogenesis attract growing attention. In Korea, an aqueous extract from the Japanese spice bush Lindera obtusiloba is traditionally used for treatment of inflammation and prevention of liver damage. We here investigated effects of the L. obtusiloba extract on cell growth, apoptosis, Wnt signaling and differentiation of (im)mature adipocytes using 3T3-L1, an established cell line for studying adipogenesis. L. obtusiloba extract reduced the de novo DNA synthesis of 3T3-L1 preadipocytes in a concentration dependent manner with an IC(50) of ∼135 μg/ml paralleled by induction of caspase 3/7 mediated apoptosis. Hormone-induced 3T3 L1 differentiation in the presence of L. obtusiloba extract resulted in a reduced accumulation of intracellular lipid droplets by 70%, in down-regulated expression of the adipogenesis-associated proteins glucose transporter-4 and vascular endothelial growth factor, in reduced secretion of the proadipogenic matrix metalloproteinase-2, and in dampened phosphorylation of the Wnt pathway effector protein β-catenin with subsequent diminished expression of the peroxisome proliferator-activated receptor-γ. Treatment of mature adipocytes with L. obtusiloba extract also significantly reduced intracellular lipid droplets. In addition to this strong interference of L. obtusiloba extract with adipogenesis, L. obtusiloba extract exerted anti-inflammatory effects. L. obtusiloba extract significantly attenuated lipopolysaccharide- and tumor necrosis factor α-induced secretion of IL-6 by preadipocytes, thus influencing insulin resistance and inflammatory state characterizing obesity. In conclusion, extracts of L. obtusiloba should be evaluated as a potential complementary treatment option for obesity associated with the metabolic syndrome.

The podosomal-adaptor protein SH3PXD2B is essential for normal postnatal development

Podosome-type adhesions are actin-based membrane protrusions involved in cell-matrix adhesion and extracellular matrix degradation. Despite growing knowledge of many proteins associated with podosome-type adhesions, much remains unknown concerning the function of podosomal proteins at the level of the whole animal. In this study, the spontaneous mouse mutant nee was used to identify a component of podosome-type adhesions that is essential for normal postnatal growth and development. Mice homozygous for the nee allele exhibited runted growth, craniofacial and skeletal abnormalities, ocular anterior segment dysgenesis, and hearing impairment. Adults also exhibited infertility and a form of lipodystrophy. Using genetic mapping and DNA sequencing, the cause of nee phenotypes was identified as a 1-bp deletion within the Sh3pxd2b gene on mouse Chromosome 11. Whereas the wild-type Sh3pxd2b gene is predicted to encode a protein with one PX domain and four SH3 domains, the nee mutation is predicted to cause a frameshift and a protein truncation altering a portion of the third SH3 domain and deleting all of the fourth SH3 domain. The SH3PXD2B protein is believed to be an important component of podosomes likely to mediate protein-protein interactions with membrane-spanning metalloproteinases. Testing this directly, SH3PXD2B localized to podosomes in constitutively active Src-transfected fibroblasts and through its last SH3 domain associated with a transmembrane member of a disintegrin and metalloproteinase family of proteins, ADAM15. These results identify SH3PXD2B as a podosomal-adaptor protein required for postnatal growth and development, particularly within physiologic contexts involving extracellular matrix regulation.

Inhibition of adipocyte differentiation by Nur77, Nurr1, and Nor1

Members of the nuclear receptor 4A (NR4A) subgroup of nuclear receptors have been implicated in the regulation of glucose and lipid metabolism in insulin-sensitive tissues such as liver and skeletal muscle. However, their function in adipocytes is not well defined. Previous studies have reported that these receptors are rapidly up-regulated after treatment of 3T3-L1 preadipocytes with an adipogenic cocktail. We show here that although Nur77 expression is acutely induced by cAMP agonists in 3T3-L1 cells, it is not induced by other adipogenic stimuli, such as peroxisome proliferator-activated receptor-gamma ligands, nor is it induced during the differentiation of 3T3-F442A preadipocytes, suggesting that Nur77 induction is not an obligatory feature of preadipocyte differentiation. We further demonstrate that inflammatory signals that antagonize differentiation, such as TNFalpha and lipopolysaccharide, acutely induce Nur77 expression both in vitro and in vivo. We also show that NR4A expression in adipose tissue is responsive to fasting/refeeding. Retroviral transduction of each of the NR4A receptors (Nur77, Nurr1, and NOR1) into either 3T3-L1 or 3T3-F442A preadipocytes potently inhibits adipogenesis. Interestingly, NR4A-mediated inhibition of adipogenesis cannot be rescued by peroxisome proliferator-activated receptor-gamma overexpression or activation. Transcriptional profiling of Nur77-expressing preadipocytes led to the identification of gap-junction protein alpha1 (Gja1) and tolloid-like 1 (Tll1) as Nur77-responsive genes. Remarkably, retroviral expression of either Gja1 or Tll1 in 3T3-L1 preadipocytes also inhibited adipocyte differentiation, implicating these genes as potential mediators of Nur77's effects on adipogenesis. Finally, we show that Nur77 expression inhibits mitotic clonal expansion of preadipocytes, providing an additional mechanism by which Nur77 may inhibit adipogenesis.

Wdnm1-like, a new adipokine with a role in MMP-2 activation

White adipose tissue functions in energy storage and as an endocrine organ. DNA microarray analysis led us to identify Wdnm1-like, a distant member of the whey acidic protein/four-disulfide core (WAP/4-DSC) family, as a differentiation-dependent gene in white and brown adipogenesis. Wdnm1-like is a novel 6.8-kDa protein, and Western blot analysis reveals secretion into culture media. Wdnm1-like transcript is selectively expressed in adipose tissue and liver and is enriched approximately 500-fold in white adipose depots vs. brown. Cellular fractionation of WAT demonstrates Wdnm1-like transcript expression is restricted to the adipocyte population. Studies in 3T3-L1 preadipocytes, an in vitro model of white adipogenesis, indicate Wdnm1-like transcript increases within 6 h of adipogenic induction with an approximately 17,000-fold increase by day 7. Dramatic upregulation of Wdnm1-like also accompanies white adipogenesis of ScAP-23 preadipocytes and primary preadipocytes. TNF-alpha treatment of 3T3-L1 adipocytes increased Wdnm1-like transcript level 2.4-fold and was attenuated by pretreatment with the p38 MAP kinase inhibitor SB203580. A number of WAP/4-DSC family proteins function as protease inhibitors. This, taken with the role of extracellular remodeling in adipogenesis, led us to address effects of Wdnm1-like on matrix metalloproteinase (MMP) activity. Gelatin zymography of HT1080 fibrosarcoma cells transfected with a Wdnm1-like expression construct revealed markedly increased levels of active MMP-2. Our findings identify a new member of the adipocyte "secretome" that functions to enhance MMP-2 activity. We postulate that Wdnm1-like may play roles in remodeling of the extracellular milieu in adipogenesis, as well as in tumor microenvironments where adipocytes are key stromal components.

The roles of HIV-1 proteins and antiretroviral drug therapy in HIV-1-associated endothelial dysfunction

Since the emergence of highly active antiretroviral therapy (HAART), human immunodeficiency virus-1 (HIV-1)-infected patients have demonstrated dramatic decreases in viral burden and opportunistic infections, and an overall increase in life expectancy. Despite these positive HAART-associated outcomes, it has become increasingly clear that HIV-1 patients have an enhanced risk of developing cardiovascular disease over time. Clinical studies are instrumental in our understanding of vascular dysfunction in the context of HIV-1 infection. However, most clinical studies often do not distinguish whether HIV-1 proteins, HAART, or a combination of these 2 factors cause cardiovascular complications. This review seeks to address the roles of both HIV-1 proteins and antiretroviral drugs in the development of endothelial dysfunction because endothelial dysfunction is the hallmark initial step of many cardiovascular diseases. We analyze recent in vitro and in vivo studies examining endothelial toxicity in response to HIV-1 proteins or in response to the various classes of antiretroviral drugs. Furthermore, we discuss the multiple mechanisms by which HIV-1 proteins and HAART injure the vascular endothelium in HIV-1 patients. By understanding the molecular mechanisms of HIV-1 protein- and antiretroviral-induced cardiovascular disease, we may ultimately improve the quality of life of HIV-1 patients through better drug design and the discovery of new pharmacological targets.

How HIV protease inhibitors promote atherosclerotic lesion formation

PURPOSE OF REVIEW

One of the aims of this review is to summarize recent clinical approaches used to determine the role of HIV protease inhibitors in the development of cardiovascular disease. Another aim is to discuss possible molecular mechanisms whereby HIV protease inhibitors may promote atherogenesis.

RECENT FINDINGS

Several clinical studies have recently used ultrasonography to demonstrate increased intimal medial thickness and alterations in the structural characteristics of epi-aortic lesions in patients receiving HIV protease inhibitors. Molecular studies have indicated that several mechanisms are likely involved in mediating the effects of protease inhibitors. Possible mechanisms include inhibition of the proteasome, increased CD36 expression in macrophage, inhibition of lipoprotein lipase-mediated lipolysis, decreased adiponectin levels, and dysregulation of the NF-kappaB pathway.

SUMMARY

The currently available data strongly suggest that HIV protease inhibitors negatively impact the cardiovascular system. As is often the case with complex diseases like atherosclerosis it appears that HIV protease inhibitors affect the cardiovascular system through several distinct mechanisms by affecting various components of the arterial wall directly or indirectly by influencing lipoprotein and glucose metabolism of the body.

Macrophages transmit human immunodeficiency virus type 1 products to CD4-negative cells: involvement of matrix metalloproteinase 9

It was previously reported that human immunodeficiency virus type 1 (HIV-1) spreads in CD4 lymphocytes through cell-to-cell transmission. Here we report that HIV-1-infected macrophages, but not lymphocytes, transmit HIV-1 products to CD4-negative cells of either epithelial, neuronal, or endothelial origin in the absence of overt HIV-1 infection. This phenomenon was detectable as early as 1 h after the start of cocultivation and depended on cell-to-cell contact but not on the release of viral particles from donor cells. Transfer of HIV-1 products occurred upon their polarization and colocalization within zones of cell-to-cell contact similar to virological synapses. Neither HIV-1 Env nor Nef expression was required but, interestingly, we found that an HIV-1-dependent increase in matrix metalloproteinase 9 production from donor cells significantly contributed to the cell-to-cell transmission of the viral products. The macrophage-driven transfer of HIV-1 products to diverse CD4-negative cell types may have a significant role in AIDS pathogenesis.

Subcutaneous fat in normal and diseased states

The quest for effective strategies to treat obesity has propelled fat research into an exploration of the molecular processes that drive adipocyte formation, and hence body fat mass. The development of obesity is dependent on the coordinated interplay of adipocyte hypertrophy (increased fat cell size), adipocyte hyperplasia (increased fat cell number), and angiogenesis. Evidence suggests that adipocyte hyperplasia, or adipogenesis, occurs throughout life, both in response to normal cell turnover as well as in response to the need for additional fat mass stores that arises when caloric intake exceeds nutritional requirements. Adipogenesis involves two major events-the recruitment and proliferation of adipocyte precursor cells, called preadipocytes, followed by the subsequent conversion of preadipocytes, or differentiation, into mature fat cells. In vitro studies using experimental and primary preadipocyte cell lines have uncovered the mechanisms that drive the adipogenic process, a tightly controlled sequence of events guided by the strict temporal regulation of multiple inhibitory and stimulatory signaling events involving regulators of cell-cycle functions and differentiation factors. This article reviews the current understanding of adipogenesis with emphasis on the various stages of adipocyte development; on key hormonal, nutritional, paracrine, and neuronal control signals; as well as on the components involved in cell-cell or cell-matrix interactions that are pivotal in regulating fat cell formation. Special consideration is given to clinical applications derived from adipogenesis research with impact on medical, surgical and cosmetic fields.

Inhibition of human preadipocyte proteasomal activity by HIV protease inhibitors or specific inhibitor lactacystin leads to a defect in adipogenesis, which involves matrix metalloproteinase-9

In a previous publication, we reported that human immunodeficiency virus (HIV) protease inhibitors (PIs) inhibited the differentiation of human preadipocytes in primary culture, reducing the expression and secretion of matrix metalloproteinase 9 (MMP-9). The present work was performed to clarify this mechanism. Interestingly, HIV-PIs have been reported to be inhibitors of the proteasome complex, which is known to regulate nuclear factor (NF)-kappaB activation and transcription of its target genes, among them MMP-9. We thus investigated the potential involvement of the proteasome in the antiadipogenic effects of HIV-PIs. The effect of four HIV-PIs was tested on preadipocyte proteasomal activity, and chronic treatment with the specific proteasome inhibitor lactacystin was performed to evaluate alterations of adipogenesis and MMP-9 expression/secretion. Finally, modifications of the NF-kappaB pathway induced by either HIV-PIs or lactacystin were studied. We demonstrated that preadipocyte proteasomal activity was decreased by several HIV-PIs and that chronic treatment with lactacystin mimicked the effects of HIV-PIs by reducing adipogenesis and MMP-9 expression/secretion. Furthermore, we observed an intracellular accumulation of the NF-kappaB inhibitor, IkappaBbeta, with chronic treatment with HIV-PIs or lactacystin as well as a decrease in MMP-9 expression induced by acute tumor necrosis factor-alpha stimulation. These results indicate that inhibition of the proteasome by specific (lactacystin) or nonspecific (HIV-PIs) inhibitors leads to a reduction of human adipogenesis, and they therefore implicate deregulation of the NF-kappaB pathway and the related decrease of the key adipogenic factor, MMP-9. This study adds significantly to recent reports that have linked HIV-PI-related lipodystrophic syndrome with altered proteasome function, endoplasmic reticulum stress, and metabolic disorders.

Role of the fibrinolytic and matrix metalloproteinase systems in development of adipose tissue

Obesity is a common disorder and related diseases such as diabetes, atherosclerosis, hypertension, cardiovascular disease and cancer are a major cause of mortality and morbidity in Western-type societies. Development of obesity is associated with extensive modifications in adipose tissue involving adipogenesis, angiogenesis and extracellular matrix proteolysis. The fibrinolytic (plasminogen/plasmin) and matrix metalloproteinase (MMP) systems cooperate in these processes. A nutritionally induced obesity model in transgenic mice has been used extensively to study the role of the fibrinolytic and MMP systems in the development of obesity. These studies support a role of both systems in adipogenesis and obesity; the role of specific members of these families, however, remains to be determined.

Role and function of matrix metalloproteinases in the differentiation and biological characterization of mesenchymal stem cells

Matrix metalloproteinases (MMPs), known as matrixins, are Ca- and Zn-dependent endoproteinases involved in a wide variety of developmental and disease-associated processes, proving to be crucial protagonists in many physiological and pathological mechanisms. The ability of MMPs to alter, by limited proteolysis and through the fine control of tissue inhibitors of metalloproteinases, the activity or function of numerous proteins, enzymes, and receptors suggests that they are also involved in various important cellular functions during development. In this review, we focus on the differentiation of mesenchymal stem cells (including those of the myoblastic, osteoblastic, chondroblastic, neural, and apidoblastic lineages) and the possible, if unexpected, biological significance of MMPs in its regulation. The MMP system has been implicated in several differentiation events that suggests that it mediates the proliferative and prodifferentiating effect of the matrixin proteolytic cascade. We summarize these regulatory effects of MMPs on the differentiation of mesenchymal stem cells and hypothesize on the function of MMPs in the stem cell differentiation processes.