Adipose tissue‐specific modulation of galectin expression in lean and obese mice: Evidence for regulatory function

Objective:

Galectins (Gal) exert many activities, including regulation of inflammation and adipogenesis. We evaluated modulation of Gal‐1, ‐3, ‐9 and ‐12 in visceral (VAT) and subcutaneous (SAT) adipose tissue in mice.

Design and Methods:

We used two mouse models of obesity, high‐fat diet induced obesity (DIO) and ob/ob mice. We also evaluated the response of Gal‐1 KO mice to DIO.

Results:

Both age and diet modulated expression of galectins, with DIO mice having higher serum Gal‐1 and Gal‐3 versus lean mice after 13‐17 weeks of high‐fat diet. In DIO mice there was a progressive increase in expression of Gal‐1 and Gal‐9 in SAT, whereas Gal‐3 increased in both VAT and SAT. Expression of Gal‐12 declined over time in VAT of DIO mice, similar to adiponectin. Obesity lead to increased production of Gal‐1 in adipocytes, whereas the increased Gal‐3 and Gal‐9 of obesity mostly derived from the stromovascular fraction. Expression of Gal‐12 was restricted to adipocytes. There was increased production of Gal‐3 and Gal‐9, but not Gal‐1, in CD11c^? and CD11c⁺ macrophages from VAT of DIO versus lean mice. Expression of Gal‐1, ‐3 and ‐12 in VAT and SAT of ob/ob mice followed a trend comparable to DIO mice. Rosiglitazone reduced serum Gal‐1, but not Gal‐3 and modulated expression of Gal‐3 in VAT and Gal‐9 and Gal‐12 in SAT of DIO mice. High‐fat feeding lead to increased adiposity in Gal‐1 KO versus WT mice, with loss of correlation between leptin and adiposity and no alterations in glucose and insulin levels.

Conclusions:

Obesity leads to differential modulation of Gal‐1, 3, 9 and 12 in VAT and SAT, with Gal‐1 acting as a modulator of adiposity.

     

High dietary fat exacerbates arsenic-induced liver fibrosis in mice

Many factors could potentially affect the process of arsenic-induced liver fibrosis. The present study was undertaken to examine the effect of high fat diet on arsenic-induced liver fibrosis and preneoplastic changes. Mice were given sodium arsenite (As3+, 200 ppm) or sodium arsenate (As5+, 200 ppm) in the drinking water for 10 months, and provided a normal diet or a diet containing 20% added fat. Serum aspartate aminotransferase (AST), indicative of liver injury, was elevated in both arsenite and arsenate groups, and a high fat diet further increased these levels. Histopathology (H&E and Masson stain) showed that liver inflammation, steatosis (fatty liver), hepatocyte degeneration, and fibrosis occurred with arsenic alone, but their severity was markedly increased with the high fat diet. Total liver RNA was isolated for real-time RT-PCR analysis. Arsenic exposure increased the expression of inflammation genes, such as TNF-alpha, IL-6, iNOS, chemokines, and macrophage inflammatory protein-2. The expression of the stress-related gene heme oxygenase-1 was increased, while metallothionein-1 and GSH S-transferase-pi were decreased when arsenic was combined with the high fat diet. Expression of genes related to liver fibrosis, such as procollagen-1 and -3, SM-actin and TGF-beta, were synergistically increased in the arsenic plus high fat diet group. The expression of genes encoding matrix metalloproteinases (MMP2, MMP9) and tissue inhibitors of metalloproteinases (TIMP1, TIMP2) was also enhanced, suggestive of early oncogenic events. In general, arsenite produced more pronounced effects than arsenate. In summary, chronic inorganic arsenic exposure in mice produces liver injury, and a high fat diet markedly increases arsenic-induced hepatofibrogenesis.     

Contribution of genetic and dietary insulin resistance to Alzheimer phenotype in APP/PS1 transgenic mice

According to epidemiological studies, type‐2 diabetes increases the risk of Alzheimer’s disease. Here, we induced hyperglycaemia in mice overexpressing mutant amyloid precursor protein and presenilin‐1 (APdE9) either by cross‐breeding them with pancreatic insulin‐like growth factor 2 (IGF‐2) overexpressing mice or by feeding them with high‐fat diet. Glucose and insulin tolerance tests revealed significant hyperglycaemia in mice overexpressing IGF‐2, which was exacerbated by high‐fat diet. However, sustained hyperinsulinaemia and insulin resistance were observed only in mice co‐expressing IGF‐2 and APdE9 without correlation to insulin levels in brain. In behavioural tests in aged mice, APdE9 was associated with poor spatial learning and the combination of IGF‐2 and high‐fat diet further impaired learning. Neither high‐fat diet nor IGF‐2 increased β‐amyloid burden in the brain. In male mice, IGF‐2 increased β‐amyloid 42/40 ratio, which correlated with poor spatial learning. In contrast, inhibitory phosphorylation of glycogen synthase kinase 3β, which correlated with good spatial learning, was increased in APdE9 and IGF‐2 female mice on standard diet, but not on high‐fat diet. Interestingly, high‐fat diet altered τ isoform expression and increased phosphorylation of τ at Ser202 site in female mice regardless of genotype. These findings provide evidence for new regulatory mechanisms that link type‐2 diabetes and Alzheimer pathology.     

Self‐Selected Macronutrient Diet Affects Energy and Glucose Metabolism in Brown Fat‐Ablated Mice

Objective: Obese transgenic UCP‐DTA mice have largely ablated brown adipose tissue and develop obesity and diabetes, which are highly susceptible to a high‐fat diet. We investigated macronutrient self‐selection and its effect on development of obesity, diabetes, and energy homeostasis in UCP‐DTA mice. Research Methods and Procedures: UCP‐DTA and wild‐type littermates were fed a semisynthetic macronutrient choice diet (CD) ad libitum from weaning until 17 weeks. Energy homeostasis was assessed by measurement of food intake, food digestibility, body composition, and energy expenditure. Diabetes was assessed by blood glucose measurements and insulin tolerance test. Results: Wild‐type and UCP‐DTA mice showed a high fat preference and increased energy digestion on CD compared with a low‐fat standard diet. On CD, wild‐type mice accumulated less body fat (16.9%) than UCP‐DTA (32.6%) mice, although they had a higher overall energy intake. Compared with wild‐type mice, resting metabolic rate was reduced in UCP‐DTA mice irrespective of diet. UCP‐DTA mice progressively decreased their carbohydrate intake, resulting in an almost complete avoidance of carbohydrate. UCP‐DTA mice developed severe insulin resistance but showed decreased fed and fasted blood glucose on CD. Discussion: In contrast to wild‐type mice, UCP‐DTA mice were not able to reduce their weight gain efficiency on CD. This suggests that, because of the high fat preference of the background strain and the increased metabolic efficiency, brown adipose tissue‐deficient mice still develop obesity and insulin resistance on a macronutrient CD even when decreasing overall energy intake. Through the avoidance of carbohydrates, however, they are able to maintain normoglycemia.     

Acute inflammation plays a limited role in the regulation of adipose tissue COL1A1 protein abundance

Obesity is an inflammatory condition that is also associated with increased extracellular matrix (ECM) gene expression. However, a direct link between adipose tissue inflammation and ECM gene expression has not been established. Therefore, we determined the effect of chronic inflammation induced by obesity and acute inflammation by lipopolysaccharide (LPS) challenge on ECM genes including biglycan (BGN), collagen 1A1 (COL1A1) and COL6A1, major ECM genes in adipose tissue. Male C57BL/6J mice fed either a control diet (10% fat calories) or a high-fat diet (HFD) (60% fat calories) for 6 weeks were treated with LPS or saline 24 h before sacrifice. Expression of ECM genes in the epididymal (EWAT) and subcutaneous adipose tissue (SWAT) was determined by RT-PCR and protein abundance by Western blotting. Human SWAT from lean and obese subjects was also analyzed. Increased messenger RNA (mRNA) expression of ECM genes BGN and COL1A1 was observed in the mouse EWAT after HFD (P<.05). However, reduced amount of COL1A1 protein was observed in EWAT of mice on HFD and in SWAT from obese human subjects. Acute inflammation induced BGN mRNA in EWAT, enhanced the gene expression of matrix metalloproteases (MMPs) 3 and 9. Acute inflammation also resulted in higher MMP9 gelatinolytic activity; however, this showed no association with COL1A1 protein abundance. Higher MMP2 expression in mice on HFD suggests its involvement in the reduction of COL1A1 protein abundance with HFD. Elevated MMP9 gelatinolytic activity in SWAT from obese humans indicates a prominent role for MMP9 in SWAT COL1A1 protein turnover in humans.     

Role of matrix metalloproteinases in development of diabetic nephropathy

This review considers molecular mechanisms that underlie disorders in the structure and metabolism of renal extracellular matrix in diabetic nephropathy. The contribution of the increased synthesis of renal extracellular matrix proteins in the accumulation of renal mesangial matrix is considered, and the important role of the degradation system of the extracellular matrix proteins in the development of fibrosis is also shown. Data on changes in mRNA expression for the matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) in various forms of diabetic nephropathy are presented. A correlation is established between changes in the balance of MMP proteolytic activity and TIMP activity and the accumulation of extracellular matrix.     

Absence of tissue inhibitor of metalloproteinases 3 disrupts alveologenesis in the mouse

Tissue inhibitors of metalloproteinases (TIMPs) regulate extracellular matrix (ECM) degradation by matrix metalloproteinases (MMPs) throughout lung development. We examined lungs from TIMP3 null mice and found significant air space enlargement compared with wild type (WT) animals during a time course spanning early alveologenesis (post‐partum days 1, 5, 9 and 14). Trichrome staining revealed a similar pattern of collagen distribution in the walls of nascent alveoli; however, the alveolar walls of TIMP3 mutant mice appeared to be thinner than controls. Assessment of MMP2 and MMP9 activities by gelatin zymography demonstrated a significant elevation in the active form of MMP2 at post‐partum days 1 and 5. Treatment of null pregnant dams with a broad spectrum synthetic metalloproteinase inhibitor, GM6001, on embryonic day 16.5 enhanced the formation of primitive alveoli during the saccular stage of lung development as evidenced by a partial, but significant, rescue of alveolar size in post‐partum day 1 animals. We propose that increased MMP activity in the absence of TIMP3 enhances ECM proteolysis, upsetting proper formation of primitive alveolar septa during the saccular stage of alveologenesis. Therefore, TIMP3 indirectly regulates alveolar formation in the mouse. To our knowledge, ours is the first study to demonstrate that in utero manipulation of the TIMP/MMP proteolytic axis, to specifically inhibit proteolysis, significantly affects lung development.     

Toll-like receptor 3 ablation prevented high-fat diet-induced obesity and metabolic disorder

Inflammation in insulin-sensitive tissues (e.g., liver, visceral adipose tissue [VAT]) plays a major role in obesity and insulin resistance. Recruitment of innate immune cells drives the dysregulation of glucose and lipid metabolism. We aimed to seek the role of Toll like receptor 3 (TLR3), a pattern recognition receptor involved in innate immunity, obesity and the metabolic disorder. TLR3 expression in liver and VAT from diet induced obese mice and in VAT from overweight women was examined. Body weight, glucose homeostasis and insulin sensitivity were evaluated in TLR3 wild-type and knockout (KO) mice on a chow diet (CD) or high-fat diet for 15 weeks. At euthanasia, blood was collected, and plasma biochemical parameters and adipokines were determined with commercial kits. Flow cytometry was used to measure macrophage infiltration and activation in VAT. Standard western blot, immunohistochemistry and quantative PCR were used to assess molecules in pathways about lipid and glucose metabolism, insulin and inflammation in tissues of liver and VAT. Utilizing human and animal samples, we found that expression of TLR3 was upregulated in the liver and VAT in obese mice as well as VAT in overweight women. TLR3-deficiency protected against high-fat diet induced obesity, glucose intolerance, insulin resistance and lipid accumulation. Lipolysis was enhanced in VAT and hepatic lipogenesis was inhibited in TLR3 KO animals. Macrophages infiltration into adipose tissue was attenuated in TLR3 KO mice, accompanied with inhibition of NF-κB-dependent AMPK/Akt signaling pathway. These findings demonstrated that TLR3 ablation prevented obesity and metabolic disorders, thereby providing new mechanistic links between inflammation and obesity and associated metabolic abnormalities in lipid/glucose metabolism.     

Tissue inhibitor of metalloproteinase‐2(TIMP‐2)‐deficient mice display motor deficits

The degradation of the extracellular matrix is regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Matrix components of the basement membrane play critical roles in the development and maintenance of the neuromuscular junction (NMJ), yet almost nothing is known about the regulation of MMP and TIMP expression in either the pre‐ or postsynaptic compartments. Here, we demonstrate that TIMP‐2 is expressed by both spinal motor neurons and skeletal muscle. To determine whether motor function is altered in the absence of TIMP‐2, motor behavior was assessed using a battery of tests (e.g., RotaRod, balance beam, hindlimb extension, grip strength, loaded grid, and gait analysis). TIMP‐2^?/? mice fall off the RotaRod significantly faster than wild‐type littermates. In addition, hindlimb extension is reduced and gait is both splayed and lengthened in TIMP‐2^?/? mice. Motor dysfunction is more pronounced during early postnatal development. A preliminary analysis revealed NMJ alterations in TIMP‐2^?/? mice. Juvenile TIMP‐2^?/? mice have increased nerve branching and acetylcholine receptor expression. Adult TIMP‐2^?/? endplates are enlarged and more complex. This suggests a role for TIMP‐2 in NMJ sculpting during development. In contrast to the increased NMJ nerve branching, cerebellar Purkinje cells have decreased neurite outgrowth. Thus, the TIMP‐2^?/? motor phenotype is likely due to both peripheral and central defects. The tissue specificity of the nerve branching phenotype suggests the involvement of different MMPs and/or extracellular matrix molecules underlying the TIMP‐2^?/? motor phenotype. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2006     

Type‐specific dysregulation of matrix metalloproteinases and their tissue inhibitors in end‐stage heart failure patients: relationship between MMP‐10 and LV remodelling

Although past studies observed the changes of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in end‐stage heart failure (HF) patients, a consistent and clear pattern of type‐specific MMPs and/or TIMPs has yet to be further defined. In this study, proteomic approach of human protein antibody arrays was used to compare MMP and TIMP expression levels of left ventricular (LV) myocardial samples from end‐stage HF patients due to dilated cardiomyopathy (DCM) with those from age‐ and sex‐ matched non‐failing patients. Western blot analysis, immunohistochemistry and ELISA were used for validation of our results. We observed that MMP‐10 and ‐7 abundance increased, accompanied by decreased TIMP‐4 in DCM failing hearts (n= 8) compared with non‐failing hearts (n= 8). The results were further validated in a cohort of 34 end‐stage HF patients derived from three forms of cardiomyopathies. Cardiac and plasma MMP‐10 levels were positively correlated with the LV end‐diastolic dimension in this HF cohort. In addition, we observed that insulin‐like growth factor‐2 promoted MMP‐10 production in neonatal rat cardiomyocytes. In conclusion, this study demonstrated a selective up‐regulation of MMP‐10 and ‐7 along with a discordant change of TIMP‐4, and a positive correlation between MMP‐10 levels and the degree of LV dilation in end‐stage HF patients. Our findings suggest that type‐specific dysregulation of MMPs and TIMPs is associated with LV remodelling in end‐stage HF patients, and MMP‐10 may act as a novel biomarker for LV remodelling.     

Increased expression of bFGF is associated with carotid atherosclerotic plaques instability engaging the NF‐κB pathway

Unstable atherosclerotic plaques of the carotid arteries are at great risk for the development of ischemic cerebrovascular events. The degradation of the extracellular matrix by matrix metalloproteinases (MMPs) and nitric oxide induced apoptosis of vascular smooth muscle cells (VSMCs) contribute to the vulnerability of the atherosclerotic plaques. Basic fibroblast growth factor (bFGF) through its mitogenic and angiogenic properties has already been implicated in the pathogenesis of atherosclerosis. However, its role in plaque stability remains elusive. To address this issue, a panel of human carotid atherosclerotic plaques was analysed for bFGF, FGF‐receptors‐1 and ‐2 (FGFR‐1/‐2), inducible nitric oxide synthase (iNOS) and MMP‐9 expression. Our data revealed increased expression of bFGF and FGFR‐1 in VSMCs of unstable plaques, implying the existence of an autocrine loop, which significantly correlated with high iNOS and MMP‐9 levels. These results were recapitulated in vitro by treatment of VSMCs with bFGF. bFGF administration led to up‐regulation of both iNOS and MMP‐9 that was specifically mediated by nuclear factor‐κB (NF‐κB) activation. Collectively, our data demonstrate a novel NF‐κB‐mediated pathway linking bFGF with iNOS and MMP‐9 expression that is associated with carotid plaque vulnerability.     

Effects of Pioglitazone Mediated Activation of PPAR-γ on CIDEC and Obesity Related Changes in Mice

Objective

Obesity is a metabolic disorder that can lead to high blood pressure, increased blood cholesterol and triglycerides, insulin resistance, and diabetes mellitus. The aim was to study the effects of pioglitazone mediated sensitization of peroxisome proliferator-activated receptor gamma (PPAR-γ) on the relationship of Cell death-inducing DFFA-like effector C (CIDEC) with obesity related changes in mice.

Methods

Sixty C57B/L6 mice weighing 10–12g at 3 weeks of age were randomly divided into 3 groups. Mice in Group 1 were fed on normal diet (ND) while Group 2 mice were given high fat diet (HFD), and Group 3 mice were given high fat diet and treated with Pioglitazone (HFD+P). Body weight, length and level of blood sugar were measured weekly. Quantitative real-time PCR, fluorescence microscopy, and ELISA were performed to analyze the expression of CIDEC and PPAR-γ in visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT).

Results

Body weight and length of mice increased gradually with time in all groups. Blood sugar in HFD mice started to increase significantly from the mid of late phase of obesity while pioglitazone attenuated blood sugar level in HFD+P mice. The mRNA expressions and protein levels of PPAR-γ and CIDEC genes started to increase in HFD mice as compared to ND mice and decreased gradually during the late phase of obesity in VAT. Pioglitazone enhanced the expression of PPAR-γ and CIDEC genes in HFD+P mice even during the late phase of obesity.

Conclusion

It is insinuated that VAT is associated with late phase obesity CIDEC decrease and insulin resistance, while pioglitazone enhances CIDEC through activation of PPAR-γ, increases its expression, and decreases lipolysis, hence preventing an increase of blood sugar in mice exposed to HFD.     

TFPI‐2 silencing increases tumour progression and promotes metalloproteinase 1 and 3 induction through tumour‐stromal cell interactions

Tissue factor pathway inhibitor‐2 (TFPI‐2) is a potent inhibitor of plasmin which activates matrix metalloproteinases (MMPs) involved in degradation of the extracellular matrix. Its secretion in the tumour microenvironment makes TFPI‐2 a potential inhibitor of tumour invasion and metastasis. As demonstrated in aggressive cancers, TFPI‐2 is frequently down‐regulated in cancer cells, but the mechanisms involved in the inhibition of tumour progression remained unclear. We showed in this study that stable TFPI‐2 down‐regulation in the National Cancer Institute (NCI)‐H460 non‐small cell lung cancer cell line using specific micro interfering micro‐interfering RNA promoted tumour progression in a nude mice orthotopic model that resulted in an increase in cell invasion. Moreover, TFPI‐2 down‐regulation enhanced cell adhesion to collagen IV and laminin via an increase in α₁ integrin on cell surface, and increased MMP expression (mainly MMP‐1 and ‐3) contributing to cancer cell invasion through basement membrane components. This study also reveals for the first time that pulmonary fibroblasts incubated with conditioned media from TFPI‐2 silencing cancer cells exhibited increased expression of MMPs, particularly MMP‐1, ‐3 and ‐7, that are likely involved in lung cancer cell invasion through the surrounding stromal tissue, thus enhancing formation of metastases.     

SOCS-1 deficiency does not prevent diet-induced insulin resistance

Obesity is associated with inflammation and increased expression of suppressor of cytokine signaling (SOCS) proteins, which inhibit cytokine and insulin signaling. Thus, reducing SOCS expression could prevent the development of obesity-induced insulin resistance. Using SOCS-1 knockout mice, we investigated the contribution of SOCS-1 in the development of insulin resistance induced by a high-fat diet (HFD). SOCS-1 knockout mice on HFD gained 70% more weight, displayed a 2.3-fold increase in epididymal fat pads mass and increased hepatic lipid content. This was accompanied by increased mRNA expression of leptin and the macrophage marker CD68 in white adipose tissue and of SREBP1c and FAS in liver. HFD also induced hyperglycemia in SOCS-1 deficient mice with impairment of glucose and insulin tolerance tests. Thus, despite the role of SOCS proteins in obesity-related insulin resistance, SOCS-1 deficiency alone is not able to prevent insulin resistance induced by a diet rich in fat.     

TIMP-1 promotes VEGF-induced neovascularization in the retina

Proteolysis of vascular basement membranes and surrounding extracellular matrix is a critical early step in neovascularization. It requires alteration of the balance between matrix metalloproteinases (MMPs) and proteins that bind to and inactivate MMPs, tissue inhibitors of metalloproteinases (TIMPs). TIMP-1 has been demonstrated to inhibit neovascularization in chick chorioallantoic membranes. However, TIMP-1 has also been shown to either promote or inhibit cell proliferation and migration in different settings. To determine whether genetic alteration of the MMP/TIMP-1 ratio would alter retinal neovascularization, we crossed mice that express vascular endothelial growth factor (VEGF) in photoreceptors with TIMP-1-deficient mice or mice that overexpress TIMP-1. Compared to VEGF transgene-positive/TIMP-1-sufficient mice, VEGF transgene-positive/TIMP-1-deficient mice showed smaller neovascular lesions. There was also no difference between the two groups of mice in the appearance of the neovascularization by light or electron microscopy. Compound VEGF/TIMP-1 transgenic mice had increased expression of both VEGF and TIMP-1 in the retina, and had more neovascularization than mice that had increased expression of VEGF alone. These gain- and loss-of-function data suggest that alteration of the TIMP-1/MMP ratio modulates retinal neovascularization in a complex manner and not simply by altering the proteolytic activity and thereby invasiveness of endothelial cells.     

CD36 is important for adipocyte recruitment and affects lipolysis

Objective: The scavenger receptor CD36 facilitates the cellular uptake of long‐chain fatty acids. As CD36‐deficiency attenuates the development of high fat diet (HFD)‐induced obesity, the role of CD36‐deficiency in preadipocyte recruitment and adipocyte function was set out to characterize. Design and Methods: Fat cell size and number were determined in gonadal, visceral, and subcutaneous adipose tissue of CD36^?/? and WT mice after 6 weeks on HFD. Basal lipolysis and insulin‐inhibited lipolysis were investigated in gonadal adipose tissue. Results: CD36^?/? mice showed a reduction in adipocyte size in all fat pads. Gonadal adipose tissue also showed a lower total number of adipocytes because of a lower number of very small adipocytes (diameter <50 μm). This was accompanied by an increased pool of preadipocytes, which suggests that CD36‐deficiency reduces the capacity of preadipocytes to become adipocytes. Regarding lipolysis, in adipose tissue from CD36^?/? mice, cAMP levels were increased and both basal and 8‐bromo‐cAMP stimulated lipolysis were higher. However, insulin‐mediated inhibition of lipolysis was more potent in CD36^?/? mice. Conclusions: These results indicate that during fat depot expansion, CD36‐deficiency negatively affects preadipocyte recruitment and that in mature adipocytes, CD36‐deficiency is associated with increased basal lipolysis and insulin responsiveness.     

Osteoactivin regulates head and neck squamous cell carcinoma invasion by modulating matrix metalloproteases

Nearly 60% of patients with head and neck squamous cell carcinoma (HNSCC) die of metastases or locoregional recurrence. Metastasis is mediated by cancer cell migration and invasion, which are in part dependent on extracellular matrix degradation by matrix metalloproteinases. Osteoactivin (OA) overexpression plays a role in metastases in several malignancies, and has been shown to upregulate matrix metalloproteinase (MMP) expression and activity. To determine how OA modulates MMP expression and activity in HNSCC, and to investigate OA effects on cell invasion, we assessed effects of OA treatment on MMP mRNA and protein expression, as well as gelatinase and caseinolytic activity in HNSCC cell lines. We assessed the effects of OA gene silencing on MMP expression, gelatinase and caseinolytic activity, and cell invasion. OA treatment had differential effects on MMP mRNA expression. OA treatment upregulated MMP‐10 expression in UMSCC14a (p = 0.0431) and SCC15 (p < 0.0001) cells, but decreased MMP‐9 expression in UMSCC14a cells (p = 0.0002). OA gene silencing decreased MMP‐10 expression in UMSCC12 cells (p = 0.0001), and MMP‐3 (p = 0.0005) and ‐9 (p = 0.0036) expression in SCC25 cells. In SCC15 and SCC25 cells, OA treatment increased MMP‐2 (p = 0.0408) and MMP‐9 gelatinase activity (p < 0.0001), respectively. OA depletion decreased MMP‐2 (p = 0.0023) and ‐9 (p < 0.0001) activity in SCC25 cells. OA treatment increased 70 kDa caseinolytic activity in UMSCC12 cells consistent with tissue type plasminogen activator (p = 0.0078). OA depletion decreased invasive capacity of UMSCC12 cells (p < 0.0001). OA's effects on MMP expression in HNSCC are variable, and may promote cancer cell invasion.