During the early 1970s, Danish physicians Jorn Dyerberg and colleagues observed that Greenland Eskimos consuming fatty fishes exhibited low incidences of heart disease. Fish oil is now one of the most commonly consumed dietary supplements. In 2004, concentrated fish oil was approved as a drug by the FDA for the treatment of hyperlipidemia. Fish oil contains two major omega-3 fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). With advancements in lipid concentration and purification techniques, EPA- or DHA-enriched products are now commercially available, and the availability of these components in isolation allows their individual effects to be examined. Newly synthesized derivatives and endogenously discovered metabolites of DHA exhibit therapeutic utility for obesity, metabolic syndrome and cardiovascular disease.
This review summarizes our current knowledge on the distinct effects of EPA and DHA to prevent metabolic syndrome and reduce cardiotoxicity risk. Since EPA is an integral component of fish oil, we will briefly review EPA effects, but our main theme will be to summarize effects of the DHA derivatives that are available today. We focus on using nutrition-based drug discovery to explore the potential of DHA derivatives for the treatment of obesity, metabolic syndrome and cardiovascular diseases.
The safety and efficacy evaluation of DHA derivatives will provide novel biomolecules for the drug discovery arsenal. Novel nutritional-based drug discoveries of DHA derivatives or metabolites may provide realistic and alternative strategies for the treatment of metabolic and cardiovascular disease.
cardiovascular disease; dietary supplement; docosahexaenoic acid; eicosapentaenoic acid; fish oil; metabolic syndrome; obesity
Matrix metalloproteinase (MMP)-28 regulates the inflammatory and extracellular matrix (ECM) responses in cardiac aging, but the roles of MMP-28 after myocardial infarction (MI) have not been explored.
To determine the impact of MMP-28 deletion on post-MI remodeling of the left ventricle (LV)
Methods and Results
Adult C57BL/6J wild type (WT, n=76) and MMP null (MMP-28−/−, n=86) mice of both sexes were subjected to permanent coronary artery ligation to create MI. MMP-28 expression decreased post-MI, and its cell source shifted from myocytes to macrophages. MMP-28 deletion increased day 7 mortality as a result of increased cardiac rupture post-MI. MMP-28−/− mice exhibited larger LV volumes, worse LV dysfunction, a worse LV remodeling index, and increased lung edema. Plasma MMP-9 levels were unchanged in the MMP-28−/− mice but increased in WT mice at day 7 post-MI. The mRNA levels of inflammatory and ECM proteins were attenuated in the infarct regions of MMP-28−/− mice, indicating reduced inflammatory and ECM responses. M2 macrophage activation was impaired when MMP-28 was absent. MMP-28 deletion also led to decreased collagen deposition and fewer myofibroblasts. Collagen cross-linking was impaired, due to decreased expression and activation of lysyl oxidase in the infarcts of MMP-28−/− mice. The LV tensile strength at day 3 post-MI, however, was similar between the two genotypes
MMP-28 deletion aggravated MI induced LV dysfunction and rupture, due to defective inflammatory response and scar formation by suppressing M2 macrophage activation.
Myocardial infarction; MMP-28; fibroblast; macrophage phenotype; inflammation
The extracellular matrix (ECM) provides structural support by serving as a scaffold for cells, and as such the ECM maintains normal tissue homeostasis and mediates the repair response following injury. In response to myocardial infarction (MI), ECM expression is generally upregulated in the left ventricle (LV), which regulates LV remodeling by modulating scar formation. The ECM directly affects scar formation by regulating growth factor release and cell adhesion, and indirectly affects scar formation by regulating the inflammatory, angiogenic, and fibroblast responses. This review summarizes the current literature on ECM expression patterns and fibroblast mechanisms in the myocardium, focusing on the ECM response to MI. In addition, we discuss future research areas that are needed to better understand the molecular mechanisms of ECM action, both in general and as a means to optimize infarct healing.
extracellular matrix; myocardial infarction; fibroblasts; cardiac myocytes; cell-ECM communication; proteomics
Following myocardial infarction (MI), activated macrophages infiltrate into the necrotic myocardium as part of a robust pro-inflammatory response and secrete matrix metalloproteinase-9 (MMP-9). Macrophage activation, in turn, modulates the fibrotic response, in part by stimulating fibroblast extracellular matrix (ECM) synthesis. We hypothesized that overexpression of human MMP-9 in mouse macrophages would amplify the inflammatory and fibrotic responses to exacerbate left ventricular dysfunction. Unexpectedly, at day 5 post-MI, ejection fraction was improved in transgenic (TG) mice (25±2%) compared to the wild type (WT) mice (18±2%; p<0.05). By gene expression profiling, 23 of 84 inflammatory genes were decreased in the left ventricle infarct (LVI) region from the TG compared to WT mice (all p<0.05). Concomitantly, TG macrophages isolated from the LVI, as well as TG peritoneal macrophages stimulated with LPS, showed decreased inflammatory marker expression compared to WT macrophages. In agreement with attenuated inflammation, only 7 of 84 cell adhesion and ECM genes were increased in the TG LVI compared to WT LVI, while 43 genes were decreased (all p<0.05). These results reveal a novel role for macrophage-derived MMP-9 in blunting the inflammatory response and limiting ECM synthesis to improve left ventricular function post-MI.
myocardial infarction; matrix metalloproteinase-9; extracellular matrix; inflammation; cardiac remodeling; mice; macrophage
About 6 million Americans suffer from heart failure and 70% of heart failure cases are caused by myocardial infarction (MI). Following myocardial infarction, increased cytokines induce two major types of macrophages: classically activated macrophages which contribute to extracellular matrix destruction and alternatively activated macrophages which contribute to extracellular matrix construction. Though experimental results have shown the transitions between these two types of macrophages, little is known about the dynamic progression of macrophages activation. Therefore, the objective of this study is to analyze macrophage activation patterns post-MI.
We have collected experimental data from adult C57 mice and built a framework to represent the regulatory relationships among cytokines and macrophages. A set of differential equations were established to characterize the regulatory relationships for macrophage activation in the left ventricle post-MI based on the physical chemistry laws. We further validated the mathematical model by comparing our computational results with experimental results reported in the literature. By applying Lyaponuv stability analysis, the established mathematical model demonstrated global stability in homeostasis situation and bounded response to myocardial infarction.
We have established and validated a mathematical model for macrophage activation post-MI. The stability analysis provided a possible strategy to intervene the balance of classically and alternatively activated macrophages in this study. The results will lay a strong foundation to understand the mechanisms of left ventricular remodelling post-MI.
Conjugated linoleic acid (CLA) has been shown to positively influence calcium and bone metabolism. Earlier, we showed that CLA (equal mixture of c9t11-CLA and t10c12-CLA) could protect age-associated bone loss by modulating inflammatory markers and osteoclastogenesis. Since, c9t11-CLA and t10c12-CLA isomers differentially regulate functional parameters and gene expression in different cell types, we examined the efficacy of individual CLA isomers against age-associated bone loss using 12 months old C57BL/6 female mice fed for 6 months with 10% corn oil (CO), 9.5% CO + 0.5% c9t11-CLA, 9.5% CO + 0.5% t10c12-CLA or 9.5% CO + 0.25% c9t11-CLA + 0.25% t10c12-CLA. Mice fed a t10c12-CLA diet maintained a significantly higher bone mineral density (BMD) in femoral, tibial and lumbar regions than those fed CO and c9t11-CLA diets as measured by dual-energy-x-ray absorptiometry (DXA). The increased BMD was accompanied by a decreased production of osteoclastogenic factors i.e. RANKL, TRAP5b, TNF-alpha and IL-6 in serum. Moreover, a significant reduction of high fat diet-induced bone marrow adiposity was observed in t10c12-CLA fed mice as compared to that of CO and c9t11-CLA fed mice, as measured by Oil-Red-O staining of bone marrow sections. In addition, a significant reduction of osteoclast differentiation and bone resorbing pit formation was observed in t10c12-CLA treated RAW 264.7 cell culture stimulated with RANKL as compared to that of c9t11-CLA and linoleic acid treated cultures. In conclusion, these findings suggest that t10c12-CLA is the most potent CLA isomer and it exerts its anti-osteoporotic effect by modulating osteoclastogenesis and bone marrow adiposity.
Conjugated linoleic acids; Aging; Inflammation; bone resorption; Cytokines; Cell differentiation
The inverse relationship between fat in bone marrow and bone mass in the skeleton of aging subjects is well-known. However, there is no precise therapy for the treatment of bone marrow adiposity. We investigated the ability of conjugated linoleic acid (CLA) and fish oil (FO), alone or in combination, to modulate bone loss using 12 months old C57Bl/6J mice fed 10% corn oil (CO) diet as control or supplemented with 0.5% CLA or 5% FO or 0.5% CLA+5% FO for 6 months. We found, CLA fed mice exhibited reduced body weight, body fat mass (BFM), and enhanced hind leg lean mass (HLLM) and bone mineral density (BMD) in different regions measured by DXA; however, associated with fatty liver and increased insulin resistance; whereas, FO fed mice exhibited enhanced BMD, improved insulin sensitivity, with no changes in BFM and HLLM. Interestingly, CLA+FO fed mice exhibited reduced body weight, BFM, PPARγ and cathepsin K expression in bone marrow with enhanced BMD and HLLM. Moreover, CLA+FO supplementation reduced liver hypertrophy and improved insulin sensitivity with remarkable attenuation of bone marrow adiposity, inflammation and oxidative stress in aging mice. Therefore, CLA with FO combination might be a novel dietary supplement to reduce fat mass and improve BMD.
Conjugated linoleic acid; bone adiposity; fat mass; fish oil; obesity
Clinical studies suggest that rosiglitazone (RSG) treatment may increase the incidence of heart failure in diabetic patients. In this study, we examined whether a high corn oil diet with RSG treatment in insulin resistant aging mice exerted metabolic and pro-inflammatory effects that stimulate cardiac dysfunction. We also evaluated whether fish oil attenuated these effects. Female C57BL/6J mice (13 months old) were divided into 5 groups: (1) lean control (LC), (2) corn oil, (3) fish oil, (4) corn oil + RSG and (5) fish oil + RSG. Mice fed a corn oil enriched diet and RSG developed hypertrophy of the left ventricle (LV) and decreased fractional shortening, despite a significant increase in total body lean mass. In contrast, LV hypertrophy was prevented in RSG treated mice fed a fish oil enriched diet. Importantly, hyperglycemia was controlled in both RSG groups. Further, fish oil + RSG decreased LV expression of atrial and brain natriuretic peptides, fibronectin and the pro-inflammatory cytokines interleukin-6 and tumor necrosis factor-α, concomitant with increased interleukin-10 and adiponectin levels compared to the corn oil + RSG group. Fish oil + RSG treatment suppressed inflammation, increased serum adiponectin, and improved fractional shortening, attenuating the cardiac remodeling seen in the corn oil + RSG diet fed C57BL/6J insulin resistant aging mice. Our results suggest that RSG treatment has context-dependent effects on cardiac remodeling and serves a negative cardiac role when given with a corn oil enriched diet.
Aging; Corn oil; Fish oil; Cardiac remodeling; Inflammation; Left ventricle hypertrophy; Rosiglitazone
Clinical evidence indicates that fat is inversely proportional to bone mass in elderly obese women. However, it remains unclear whether obesity accelerates bone loss. In this report we present evidence that increased visceral fat leads to inflammation and subsequent bone loss in 12-month-old C57BL/6J mice that were fed 10% corn oil (CO)-based diet and a control lab chow (LC) for 6 months. As expected from our previous work, CO-fed mice demonstrated increased visceral fat and enhanced total body fat mass compared to LC. The adipocyte-specific PPARγ and bone marrow (BM) adiposity were increased in CO-fed mice. In correlation with those modifications, inflammatory cytokines (IL-1β, IL-6, TNF-α) were significantly elevated in COfed mice compared to LC-fed mice. This inflammatory BM microenvironment resulted in increased superoxide production in osteoclasts and undifferentiated BM cells. In CO-fed mice, the increased number of osteoclasts per trabecular bone length and the increased osteoclastogenesis assessed ex-vivo suggest that CO diet induces bone resorption. Additionally, the up-regulation of osteoclast-specific cathepsin k and RANKL expression and down-regulation of osteoblast-specific RUNX2/Cbfa1 supports this bone resorption in CO-fed mice. Also, COfed mice exhibited lower trabecular bone volume in the distal femoral metaphysis and had reduced OPG expression. Collectively, our results suggest that increased bone resorption in mice fed a CO-enriched diet is possibly due to increased inflammation mediated by the accumulation of adipocytes in the BM microenvironment. This inflammation may consequently increase osteoclastogenesis, while reducing osteoblast development in CO-fed mice.
Aging; adipocytes; bone marrow adiposity; obesity; osteoporosis; visceral fat
Osteoporosis and obesity remain a major public health concern through its associated fragility and fractures. Several animal models for the study of osteoporotic bone loss, such as ovariectomy (OVX) and denervation, require unique surgical skills and expensive set up. The challenging aspect of these age-associated diseases is that no single animal model exactly mimics the progression of these human-specific chronic conditions. Accordingly, to develop a simple and novel model of post menopausal bone loss with obesity, we fed either a high fat diet containing 10% corn oil (CO) or standard rodent lab chow (LC) to 12 month old female C57Bl/6J mice for 6 months. As a result, CO fed mice exhibited increased body weight, total body fat mass (BFM), abdominal fat mass and reduced bone mineral density (BMD) in different skeletal sites measured by Dual Energy X-ray Absorptiometry (DXA). We also observed that decreased bone mineral density (BMD) with age in CO fed obese mice was accompanied by increased bone marrow adiposity, up-regulation of PPARγ, cathepsin k and increased pro-inflammatory cytokines (IL-6 and TNF-α) in bone marrow and splenocytes, when compared to that of LC fed mice. Therefore, this appears to be a simple, novel and convenient age-associated model of post menopausal bone loss, in conjunction with obesity, which can be used in pre-clinical drug discovery to screen new therapeutic drugs or dietary interventions for the treatment of obesity and osteoporosis in the human population.
Adipocytes; animal model; bone adiposity; fat mass; obesity; osteoporosis; pro-inflammatory cytokines
The therapeutic efficacy of individual components of fish oils (FO) in various human inflammatory diseases still remains unresolved, possibly due to low levels of n-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) or lower ratio of DHA to EPA. Since FO enriched with DHA (FO-DHA) or EPA (FO-EPA) has become available recently, we investigated their efficacy on survival and inflammatory kidney disease in a well-established animal model of human Systemic Lupus Erythematosus (SLE). Results show for the first time that FO-DHA dramatically extends both the median (658 days) and maximal (848 days) lifespan of (NZB × NZW)F1 (B × W) mice. In contrast, FO-EPA fed mice had a median and maximal lifespan of ~384 and 500 days, respectively. Investigations into possible survival mechanisms revealed that FO-DHA (Vs. FO-EPA) lowers serum anti-dsDNA antibodies, IgG deposition in kidneys, and proteinuria. Further, FO-DHA lowered LPS-mediated increases in serum IL-18 levels and caspase-1-dependent cleavage of pro-IL-18 to mature IL-18 in kidneys. Moreover, FO-DHA suppressed LPS-mediated PI3K, Akt, and NF-κB activations in kidney. These data indicate that DHA, but not EPA, is the most potent n-3 fatty acid that suppresses glomerulonephritis and extends lifespan of SLE-prone short-lived B × W mice, possibly via inhibition of IL-18 induction and IL-18-dependent signaling.
In this study, we examined the effect of CLA isomers in preventing age-associated muscle loss and the mechanisms underlying this effect, using 12 months old C57BL/6 mice fed 10% corn oil (CO) or a diet supplemented with 0.5% c9t11-CLA, t10c12-CLA or c9t11-CLA+t10c12-CLA (CLA-mix) for 6 months. Both t10c12-CLA and CLA-mix groups showed significantly higher muscle mass, as compared to CO and c9t11-CLA groups, measured by dual-energy-Xray-absorptiometry and muscle wet weight. Enhanced mitochondrial ATP production, with higher membrane potential, and elevated muscle antioxidant enzymes (catalase and glutathione peroxidase) production, accompanied by slight increase in H2O2 production was noted in t10c12-CLA and CLA-mix groups, as compared to that of CO and c9t11-CLA groups. Oxidative stress, as measured by serum malondialdehyde and inflammation, as measured by LPS-treated splenocyte IL-6 and TNF-alpha, were significantly less in CLA isomers groups. Thus, CLA may be a novel dietary supplement that will prevent sarcopenia by maintaining redox balance during aging.
Lipid; sarcopenia; aging; redox balance; oxidative stress; inflammation
Both n-3 fatty acids (FA) and calorie-restriction (CR) are known to exert anti-inflammatory and anti-oxidative effects in animals and humans. In this study, we investigated the synergistic anti-inflammatory and anti-oxidative capacity of n-3 FA and CR using Fat-1 transgenic mice (Fat-1) that are capable of converting n-6 FA to n-3 FA endogenously. Wild type (WT) and Fat-1 mice were maintained on ad libitum (AL) or CR (40% less than AL) AIN-93 diet supplemented with 10% corn oil (rich in n-6 FA) for 5 months. Significantly lower levels of n-6/n-3 FA ratio were observed in serum, muscle and liver of Fat-1 mice fed AL or CR as compared to that of WT mice fed AL or CR. Muscle catalase (CAT), super oxide dismutase (SOD), glutathione peroxidase (GPX) activities, and liver CAT and SOD activities were found higher in Fat-1 mice as compared to that of WT mice. These activities were more pronounced in Fat-1/CR group as compared to other groups. Serum pro-inflammatory markers, such as tumor necrosis factor (TNF)α, interleukin (IL)-1β and IL-6 were found lower in Fat-1 mice, as compared to that of WT mice. This anti-inflammatory effect was also more pronounced in Fat-1/CR group as compared to that of other groups. Furthermore, significantly higher levels of peroxisome proliferator-activated receptor (PPA R)gamma and life prolonging gene, sirtuin (SIRT)-1 expression were found in liver of Fat-1/CR mice, as compared to that of WT/CR mice. These data suggest that n-3 FA along with moderate CR may prolong lifespan by attenuating inflammation and oxidative stress.
lipids; n-3 fatty acids; calorie restriction; inflammation; oxidative stress; aging; TNFα; IL-6; IL-1β; PPARγ; SIRT-1